(High Blood Glucose)

Causes, Symptoms,
Treatment & Prevention

Islets of Hope Publication HG-3-2006
You may use and distribute this information freely, but please reference www.IsletsofHope.com

Summary of Hyperglycemia Symptoms

Onset:  Over time; hours or days.

Causes:  Too little insulin, stress, illness, dehydration, exercise or inactivity, too much food, certain medications, or a combination of these things.

Increased thirst and urination
Urine may contain ketones
Labored breathing, fatigue
Increase in appetite, or decrease in appetite
Headache, stomachache, general aches and pain
Changes in behavior or temperament

ALERT:  Untreated highs can lead to diabetic ketoacidiosis (DKA) which can result in coma and/or death.  Over time, high blood glucose damages nerves and organs and disrupt normal digestive system processes.

Important Medical Disclaimer

All material found in this publication is intended to provide you with general information and should in no way be used as a substitute for professional medical care or advice.


Hyperglycemia (Low Blood Glucose)
Causes, Symptoms,
Treatment & Prevention

Islets of Hope Publication HG-3-2006

Table of Contents


  3      About Hyperglycemia 
  3      Normal & Target Blood Glucose Levels
   4      Symptoms of Hypoglycemia

   5     Causes of Hyperglycemia
   5      Diabetes-Related Hyperglycemia
   6      Non-Diabetes Related Hyperglycemia
   6      Hyperglycemia Related to Insulin Pump Use
   6      Hyperglycemia Related to Shot Therapy
   6      Bad Insulin

   7     Causes of Fasting & Nightime Hyperglycemia
   7      High-Fat Induced Hyperglycemia
   7      The Dawn Effect (or, Dawn Phenomenon)
   7      The Simogyi Effect (Rebound Hyperglycemia)
   7      High-Fat Meals & Snacks

   8     Treatment for Hyperglycemia
   8      When is it safe to treat hyperglycemia according to my pre-determined diabetes care plan?
   8      When is it not safe to treat hyperglycemia without calling the doctor?
   8      When to Call Your Doctor
   9      Treating Morning Hyperglycemia

  9      Preventing Hyperglycemia
 Preventing Hyperglycemia During the Day
  9       For all Persons on Insulin
 11      For Those on Shot Therapy

 11      For Insulin Pumpers
 11      Preventing Hyperglycemia During the Night

12     Complications of Hyperglycemia


About Hyperglycemia

Hyperglycemia, occurs when your blood glucose (blood sugar) level rises too high. Low blood glucose (hypoglycemia) presents and immediate danger, but high blood glucose is another story. Short-term elevated blood glucose levels are not great, but unfortunately, a part of diabetes that sometimes cannot be avoided.  

Reasonable high blood glucose levels short-term (i.e., after meals) don't present imminent danger (the exception being if a diabetic is in a state of diabetic ketoacidosis ([DKA]).  But over time, high blood glucose levels destroy nerves and eventually damage organs and tissues throughout the body.  Once this damage is done, serious life-long problems can occur.  

Normal and Target Blood Glucose Ranges (mg/dL)

Normal blood glucose levels in people who do not have diabetes:
Upon waking (fasting) 70 to 110

After meals

70 to 140
Target blood glucose levels in people who have diabetes:
Before meals 90 to 130
1 to 2 hours after the start of a meal less than 180
Hypoglycemia (low blood glucose) 70 or below

Important Note:  Your doctor may provide you with different target ranges so be sure to know he/she recommends for your blood glucose levels.

Glucose levels are measured in either:

  • Milligrams per deciliter (mg/dL), in the United States and other countries (Myanmar, Liberia) that do not yet use the International or "Metric" System of measurement; or,
  • Millimoles per liter (mmol/L)


  •  72 mg/dL = 4 mmol/L
  •  90 mg/dL = 5 mmol/L
  • 108 mg/dL = 6 mmol/L
  • 126 mg/dL = 7 mmol/L

In fasting non-diabetic adults, blood plasma glucose should not exceed 125 mg/dL (7 mmol/L).

Glucose levels vary before and after meals, at various times of day, as well as throughout the night in persons with diabetes as well as in non-diabetics.  If you have trouble meeting your target blood glucose levels you may need to make changes in your diabetes care plan. Call your doctor to learn what adjustments are appropriate for your individual needs.

Symptoms of Hyperglycemia (High Blood Glucose)

It is important to remember that people can react differently to high blood glucose levels.  Generally, symptoms of hyperglycemia include:

  • Polyphagia (frequent hunger, especially excessive hunger)
  • Polydipsia (frequent thirst, especially excessive thirst)
  • Polyuria (frequent urination, especially excessive urination)

Other symptoms of diabetic hyperglycemia may include:

  • Blurred vision
  • Fatigue
  • Weight loss
  • Poor wound healing (cuts, scrapes, etc.)
  • Dry mouth
  • Dry or itchy skin
  • Impotence (male)
  • Recurrent infections such as vaginal yeast infections, groin rash, or external ear infections

These symptoms do not normally occur with acute non-diabetic hyperglycemia because generally in non-diabetics blood glucose levels do not remain elevated long enough.  But some problems may occur in non-diabetic hyperglycemia if it remains chronic.

Weight loss can be a sign of type 1 diabetes.  Weight loss almost never happens in chronic non-diabetic hyperglycemia (especially if the hyperglycemia is caused by obesity).  Instead, the non-diabetic person either maintains a stable obese weight, or gains weight. This is one of the ways non-diabetic hyperglycemia can be distinguished from diabetic hyperglycemia in which a person experiences weight loss due to insufficient levels of insulin.

Causes of Hyperglycemia

Diabetes-Related Hyperglycemia

  • Too little insulin either as a food or correction bolus, or basal (background) insulin
  • Poorly time insulin injection or pump bolus
  • Stress (even seeing and being attracted to someone can elevate blood glucose!)
  • Illness
  • Dehydration
  • Inactivity (being sedentary)
  • Too much food
  • High fat food meals
  • The Dawn Effect
  • The Simogyi Effect
  • High altitude
  • Insulin resistance or not rotating injection sites often enough
  • Exercising without sufficient water, insulin or snacks
  • Certain medications, including steroids, or
  • A combination of these things.  

Non-Diabetic Hyperglycemia

The most common cause of chronic non-diabetic hyperglycemia is obesity, the cure for which is proper diet and exercise to reduce the body's excess white fat reserves. Excessive fat interferes with the body's ability to properly absorb and use insulin that is otherwise produced in sufficient quantity (insulin resistance).

Chronic non-diabetic hyperglycemia can produce some of the same complications as diabetic hyperglycemia.  Although some of the complications of diabetes mellitus (especially type 1) can occur even if blood sugar levels are kept under control, chronic hyperglycemia is almost a guarantee of developing some type of long-term complication.

Certain eating disorders can produce acute non-diabetic hyperglycemia, as in the binge phase of bulimia nervosa.  This is when the person consumes an large number of calories at once, frequently from foods that are high in both carbohydrates and fat.

Other possible causes of elevated blood sugars include:

  • Gastroparesis (delayed emptying of stomach contents)
  • Cyclical Vomiting Syndrome (CVS)
  • Medications including steroids, and
  • Illness  

Hyperglycemia Related to Insulin Pump Use

If you are on an insulin pump and have two or more readings in a row that are high, suspect your insertion site is not working properly or your insulin is bad and the pump cartridge needs to be changed.  Take an injection of insulin via syringe and change out your site and cartridge.  You could do these things one at a time to help determine what the exact cause is, but why waste time in a hyperglycemic range when you could be damaging your body?  If you continue to have high blood glucose, call your doctor for instructions.

Hyperglycemia may result from:

Incorrect Basal Settings.  If you are on an insulin pump, you will set basal insulin rates.  Basal (or background insulin) administered through a pump consists of small, frequent amounts of insulin automatically infused into the body via a canula, (flexible tube or needle-type) inserted under the skin.  If basal rates are set too low, hyperglycemia can occur.  If they are set too high, low blood glucose can result.  Basal rates can vary according to the time of day and even day of the week.  Women may require different basal rates during their pre-period days, and on active days, many pumpers reduce their basal rates to compensate for the increase in exercise.  Your doctor can help you understand how to set basal rates, determine your insulin needs, and how to go on "mini-fasts" to test your basal rates.

Absorption Problems.  One cause of hyperglycemia on insulin pump therapy has to do with the site of the canula.  Some parts of the body are more sensitive to insulin that are other parts (i.e., a person may require less insulin when the site is placed on the thighs or buttocks than on the tummy area).  Using the same site repeatedly for canula insertion can damage tissue sensitivity and even cause scarring.  This will result in less absorption at the site and cause blood glucose to elevate.  It is important to change sites every 2-3 days and rotate the location of the needle.

Canula & Tubing Kinks.  Another cause of hyperglycemia with canula sets is when the canula "kinks" or becomes bent under the skin.  This does not occur with metal needle style canulas, but may occur with those made of flexible, soft plastic.  With both types of canulas (metal or flexible) the insertion can work loose so that it appears attached, but is not sufficiently under the skin and basal and bolus insulin leak outside the skin.  The tubing itself can also twist, interrupting proper insulin delivery.

Air Bubbles.  Hyperglycemia can result from not properly preparing your insulin cartridge.  Air bubbles in the cartridge or tubing line will not hurt you, however, it will interfere with normal insulin delivery.  Be sure that there are no air bubbles in the cartridge or tubing.

Hyperglycemia Related to Shot Therapy

Shots need to be timed.  Different types of insulin begin to work at different times, peak at different intervals, and last for varying durations.  Timing insulin and meals can be more challenging than rocket science, but, with the support and advice of your doctor and a diabetes-trained dietitian it can be done.

For those in conventional therapy (1-3 shots per day with minimal blood glucose testing of 4-5 times per day) you may be experiencing either high or low blood glucose levels throughout the day or night that can go undetected.  Be sure to have regular HbA1c tests done, the help determine if you are chronically above target range.

Other possibilities for hyperglycemia occurring while on shot therapy include:

  • Not getting all the insulin under the skin; if any leaks out hyperglycemia can result.
  • Not rotating injection sites (sites become desensitized to insulin over time).
  • Not making adjusts for using different sites (i.e., tummy injections, or other areas where there is more body fat may require more insulin than injecting into a muscle).

If you are experiencing hyperglycemia on shot therapy it is important that you speak with your doctor.  He/She can help determine if you need a different type of insulin, more insulin, or time it differently.  You should always talk with your doctor before making adjustments in your insulin dose.

Bad Insulin

Insulin should be, but does not have to be, refrigerated.  Once you remove the cap and insert a needle into the vial stopper the insulin begins to degrade.  Even if the expiration date on the package is still good, you should discard all opened insulin that has been refrigerated after 30 days.  Opened, unrefrigerated insulin should be discarded after one week.


Causes of Fasting & Nighttime Hyperglycemia

To help prevent nighttime hyperglycemia check your blood glucose at bedtime before an evening snack. If your reading is less than 120 mg/dL (or whatever pre-bedtime target your doctor has recommended), you may need to eat a larger snack containing carbohydrates and protein.  If you are too high, give yourself a correction bolus according to your diabetes care plan.

For children, or those on an insulin pump, pre-bedtime target ranges may be slightly higher.  Be sure you understand what your doctor has recommended for you and if it is not working well for you be sure to consult your doctor immediately.

You should also check your blood glucose once during each night.  If you wake in the morning with a headache, or high fasting sugars, it may be a sign that low blood glucose occurred during the night.

If you suspect low blood glucose during the night check your blood sugar at 3:00 a.m.  If your blood glucose is low at that time, you may need a smaller dose of intermediate insulin (NPH) or long-lasting insulin (Lantus® or Ultralente) in the evening.  If you are on an insulin pump your basal rates may need adjusting.  

There are three main causes of hyperglycemia during the night:  

  • Eating too much fat at dinner, or before bedtime
  • The Dawn Effect
  • Simogyi Effect  

High-Fat Induced Hyperglycemia.  Eating a high-fat snack close to bedtime (for others, even having a high-fat dinner) can cause delayed hyperglycemia.  This means that blood glucose may appear in range shortly after eating, but elevate higher over time. Fat can also keep blood glucose levels elevated many hours after eating.  During the night, when you may not be checking your blood glucose as frequently your glucose can elevate and stayed raised due to a high-fat meal.  Many people mistake a high-fat meal that induces nighttime hypoglycemia for the Dawn Effect.

The Dawn Effect (also called Dawn Phenomenon).  The dawn effect is an increase in insulin resistance (decrease in insulin sensitivity) caused by hormones released about two hours before you wake. These hormones are under the control of the pituitary gland, and thus the brain. The dawn effect is influenced by testosterone and tends to be more significant in men.  It is highly variable from person to person.

Your overnight insulin is taken to counter the dawn effect, and on average, diabetics take 20% of their insulin overnight due to an increase in metabolic needs during the night.  Persons on insulin pumps often have increased basal rates after 3 a.m. for this reason.

It is a normal occurrence in all people to experience a slight rise in blood glucose levels before rising, but this phenomenon is more pronounced in persons who need to take insulin.  The dawn effect is also the most common cause of nighttime highs.  

Simogyi Effect  (Rebound Hyperglycemia).  The Simogyi Effect occurs after a rapid drop in blood glucose levels sometime during sleep. The body responds by releasing stored glucose (released from glycogen stores) from muscles and the liver in an attempt to elevate blood glucose levels. The body may overcompensate, releasing large amounts of glycogen which results in a "rebound" effect, causing hyperglycemia. This may happen anytime during sleep, but hypoglycemia usually occurs around 3:00 a.m.  The hypoglycemic episode is followed by an elevated blood glucose level towards morning.  Inadequate food intake for exercise or too much insulin may contribute to this response.


Treatment for Hyperglycemia

Know your target range for blood glucose as set for you specifically by your doctor and follow the care plan he/she set up for you when you are experiencing hyperglycemia.  When your blood glucose is above range for 2 or 3 readings in a row call your doctor for additional instructions.

When your blood glucose is high:

  • Take an insulin correction bolus as indicated by your doctor.
  • Test blood glucose frequently to make sure levels are coming down.
  • Anytime that blood glucose is over 240 mg/dL check urine for ketones.
  • Always call your doctor when ketones are in the moderate to heavy range.
  • Limit physical activity and avoid become overheated or dehydrated.
  • Drink plenty of water or other fluids that do not contain sugar.
  • High blood sugar can trigger an increase in appetite.  Avoid eating carbohydrates and fat until glucose return to a safe range. Nibble sugar-free Jello, fat-free broth, or have a small protein-only snack.

When is it safe to treat hyperglycemia according to my pre-determined diabetes care plan?  When your blood glucose is not in range and you are not spilling moderate to heavy ketones in your urine, it is generally safe to follow instructions in your diabetes care plan provided by your doctor.  The exception might be if you were also sick, dehydrated, or under some significant stress.

When is it not safe to treat hyperglycemia without calling the doctor?  When ketones are in the moderate to heavy range, it may be a sign of diabetic ketoacidosis (DKA).  Because DKA can lead to coma and death you should always contact your doctor immediately (even after office hours) whenever you are testing positive for moderate of higher ketones.  Untreated, or, improperly treated, DKA can cause life-threatening complications.  DKA should only be treated under the strict guidance of your physician or at the hospital.

When to Call Your Doctor

Diabetic coma results when hyperglycemia leads to diabetic ketoacidosis (DKA), or hypoglycemia has led to loss of consciousness.  Diabetic coma is always a medical emergency in which the person with diabetes has become comatose (unconscious) and is in danger of dying.  Diabetic coma occurs for three reasons:

  • Severe hypoglycemia
  • Diabetic ketoacidosis advanced enough to result in unconsciousness from a combination of severe hyperglycemia, dehydration and shock, and exhaustion.  Many newly diagnosed patients are in DKA when diagnosed.  DKA is most commonly seen in persons 19 and under, but can occur at any age.
  • Hyperosmolar nonketotic coma in which extreme hyperglycemia and dehydration alone are sufficient to cause unconsciousness.


Treating Morning Hyperglycemia

If your morning glucose level is high, talk with your doctor to help determine the cause.  You may need an adjustment of your insulin in the evening -- something your doctor should help you adjust.  

If you take pills you might need another dose or an increase of the dose before bed. If you use insulin, you might need a little bit more of long acting before bed and/or some more for breakfast. If you use a pump, then it is easier and you just need to adjust your basal rate to prevent the blood glucose from rising during the night.

To help determine the cause of high morning glucose test your levels around 3 a.m.  If you are low, it could indicate the Simogyi Effect (or, rebound effect).  If you are in target most of the night but high in the morning, it is more likely the Dawn Effect.  Having a blood glucose reading at 3 a.m. is important information for your doctor to have.

You should eat breakfast every morning, about the same time of day when possible whether you are taking shots or on an insulin pump. The increase in blood glucose after you eat your breakfast will often turn off the release of glucose from liver or muscles, since your body senses the fuel is coming through food.

If your morning fasting sugar is too high, you can still eat some like protein and fewer carbs.  The key is to try and eat something.


Finally, record all your glucose readings, insulin doses, food intake, and other important items that affect blood glucose levels like stress, medication, exercise and sick days.  This information will help your diabetes care team determine what adjusts need to be made to help you get better glucose control.


Preventing Hyperglycemia


Preventing Hyperglycemia During the Day

For All People Using Insulin

Keep records and communicate with your doctor.  Keeping an accurate log book of your blood glucose levels, food eating, activities and stress or illness, and insulin and medications given is the best tool you have for understanding just how your body reacts to insulin and what your needs are.  This information is vital for your doctor to best set up, or make changes to, your diabetes care plan.

Don't use the pump as an excuse to eat all the time.  Pumping is convenient; you simply give a food bolus anytime that you eat. Persons using pumps may feel that it is okay to graze all day, or eat frequently.  Even though you may correctly bolus yourself you can still have chronically high blood glucose levels because your body needs time to react to the insulin after eating and return to target range.  Try not to eat or snack more frequently than every 2-4 hours.  If you blood glucose is still high from a recent meal or snack, wait until your glucose is back on target before eating again.

Pumps are not a cure.  Remember that an insulin pump is a tool to help you manage your diabetes; it is not a cure.  You still need to eat sensibly even while on intensive (flexible) insulin therapy like insulin pumping.

Understand how and when your insulin works.  Different types of insulin begin to work at different times, peak at different times and last for various durations.  It is as important that you understand when to take insulin as it is to know how much to take.

Plan your exercise. Exercise can either decrease, or increase, your blood glucose levels.  Always check your glucose before exercising and afterwards.  If you are not feeling well, exercising hard, or for more than an hour, stop and check your blood glucose level.  Hyperglycemia can result from exercise because the body is stressed, or becomes dehydrated.

Snack before exercising.  Many doctors recommend having a snack prior to exercising and reducing the amount of insulin given to cover the food (usually about 15 grams of carbohydrate will go uncovered if you are in your target range, but check with your doctor).  Your body needs insulin while working out as well as energy from food.  It is not wise to exercise without eating or having insulin circulating prior to exercise.

When not to exercise. If your blood glucose is over 240 mg/dL or, if you have any ketones in your urine, postpone activity until you are ketone-free and in a safe target range for exercising.

See your doctor for an HbA1c test 3-4 times per year.  It is important to understand that a person with diabetes can be in target range 4 hours after a meal, but easily climb 300-500 mg/dL 1-3 hours after eating.  Even though your target is met at 4 hours, you are still experiencing hyperglycemia that should be addressed.  Aside from potential never and organ damage, most people just don't feel good when their blood glucose levels are too high.  Regular HbA1c testing can help determine if your highs are damaging your body.

Know your target range.  Some doctors aim to keep blood glucose levels under 180 mg/dL even 1-2 after eating.  This requires dedication on the part of the patient and a good diabetes care plan from their doctor.  Make sure you inject enough insulin to cover the food you are eating and calculate any correction bolus insulin needed.

Be aware of the time of day.  Most persons are more sensitive to insulin at certain times of the day and less sensitive at other times.  You may need more insulin for breakfast than you do at dinner time.  This is not only true for calculating your insulin-to-carb ratio for food boluses, but also true for basal (background) insulin and even correction factors may be vary.

Sick days may require more or less insulin.  Illness can cause a rapid rise in blood glucose levels and the added stress from sickness or infection can increase the amount of insulin needed.  Have a sick day care plan BEFORE getting sick.  Your doctor should provide you with instructions about handling illness.  Many doctors will prescribe anti-nausea drugs to keep on hand in case of stomach flu.  Vomiting can lead to dehydration and hyperglycemia if you stop taking insulin because you cannot hold down food.  Especially when sick, your body needs insulin.

Children may need to be hospitalized if they are too sick to eat. The may require an intravenous glucose solution just so that insulin can continue to be administered.  When there is no circulating insulin in the body (either from the pancreas, shots, or an insulin pump) a person is more likely to experience DKA sooner, and at a lower glucose level than are persons who have some insulin in their body.

There seems to be one exception to the increased need for insulin during illness and that is, with a rotavirus.  Many persons with diabetes report an almost "honeymoon-like" state where they require little or no insulin other than basal insulin.  The reason is not clear, but may have to do with the extreme intestinal irritation with certain rotaviruses causes.  This can interfere with the body's ability to absorb food.  You may need reduced insulin, but only because your body is not absorbing carbohydrates. And you still need to keep circulating insulin (basal, or background) going or risk DKA.

If you find that you or your child has a flu-like illness that needs a reduction in insulin, suspect a rotavirus and call your doctor for instructions.


For Those on Conventional Shot Therapy

For persons on conventional shot therapy who may take only 1-3 injections per day, you may have been advised to only check your blood glucose 4 or 5 times per day.  If your HbA1c levels are high, it is an indication that you are not testing often enough to detect hyperglycemia.  Be sure to test 2 hours after a meal and during the night at least once to see if your glucose levels are elevated.  Report what you learn to your doctor in case changes in your diabetes care plan need to be made.


If you are on conventional shot therapy it is important to eat and take your insulin on time.  Your diabetes care program was designed with the intention that you would eat about the same time each day, and eat about the same amount at each meal and snack.  If your lifestyle is not suited for this type of therapy talk with your doctor about other options.

For Those on Insulin Pumps

Vary your basal rates. Basal rates on insulin pumps are not usually one set in using just one increment for 24 hours, but are often set at different rates for different times of the day or night.  Insulin pumps allow for greater control in covering your metabolic needs for insulin than shots because basal rates on an insulin pump can also de temporarily increased or decreased according to need.  Once a shot is injected, you can always take an additional injection but you can't turn down your basal insulin because it is already in your system.

Don't turn off your pump. Turning off your insulin pump is never a good idea even if your blood glucose levels are good.  Turning off your pump for more than an hour (only do this occasionally and as necessary) stops basal insulin from being administered.  This diminishes the amount circulating insulin in your body and can set the stage for onset of diabetic ketoacidosis (DKA).  

Unhooking your pump.  If you wish to go "unteathered" (unhook your pump) ask your doctor how to inject Lantus or other long-acting insulin to replace the basal rate function of the pump.  You can go off and on the pump (reverting to shots) but you cannot go off insulin.  Only your doctor should advise you how to switch back and forth between shots and the pump. 

Preventing Hyperglycemia During the Night

Depending upon the exact cause of your nighttime hyperglycemia, that contributed to high glucose levels in the morning, your doctor may recommend:

  • Adjusting your dosage of medication or insulin
  • Switching to a different medication
  • Testing your blood glucose around 3 a.m.
  • Changing the type and timing of your bedtime snack

If you suspect lows may be occurring during the night check your blood glucose at 3:00 a.m.  If your blood glucose is low at that time, you may need a smaller dose of intermediate insulin (NPH) or long-lasting insulin (Lantus® or Ultralente) in the evening.  If you are on an insulin pump your basal rates may need adjusting.  

Never change your insulin guidelines without discussing it with your doctor first!  


Complications of Hyperglycemia


Over time, chronic hyperglycemia is a major contributing factor towards almost all possible complications with diabetes including kidney failure, blindness, diabetic neuropathy, and heart problems.

Advanced Diabetic Ketoacidosis

A more immediate concern with untreated hyperglycemia is the possibility of diabetic ketoacidosis (DKA).  The likelihood of DKA increases when a person is sick, stressed, dehydrated, is not taking enough basal (background) insulin, or, has turned off their insulin pump completely.

Diabetic ketoacidosis (DKA), if it progresses and worsens without treatment, can eventually cause unconsciousness, from a combination of severe hyperglycemia, dehydration, shock, and exhaustion. Coma only occurs at an advanced stage, usually after 36 hours or more of vomiting and hyperventilation.

Treatment of DKA consists of isotonic fluids to rapidly stabilize the circulation, continued intravenous saline with potassium and other electrolytes to replace deficits, insulin to reverse the ketoacidosis, and careful monitoring for complications.

If you have diabetes, you should carry a medical card that asks anyone finding you unconscious to immediately call 911.