Causes of hyperglycemia

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Causes of hyperglycemia (also called high blood glucose or high blood sugar))

How Insulin Works in the Body

Glucose, a form of sugar, is an important fuel for your body. Carbohydrates are the main dietary source of glucose. Rice, potatoes, bread, tortillas, cereal, milk, fruit, beans, grains, and sweets are all examples of carbohydrate foods. After a meal, glucose molecules are absorbed into your bloodstream and carried to the cells, where they are used for energy. Insulin, a hormone produced by your pancreas, helps glucose enter cells. If you eat more glucose than your body needs at the time, your body stores the extra glucose in your liver and muscles in a form called glycogen. Your body can use the stored glycogen whenever it is needed for energy between meals. Insulin not only helps blood glucose (sugar) enter into your cells for nourishment but is also a "fat-storing" hormone because it helps glucose to be converted to fat and stored in fat cells.

When blood glucose begins to rise, insulin acts like a key to open cells so that the glucose can enter into them. Without insulin glucose remains in the blood stream and can build up to dangerous levels (hyperglycemia, or, high blood glucose/sugar). People with diabetes take insulin in order help glucose from the blood stream enter into, and nourish, cells. If a person takes too much insulin their blood glucose can go too low (see hypoglycemia and insulin shock). If you do not take enough insulin your blood glucose levels will remain too high.

The key to avoiding complications with diabetes is to manage blood glucose levels judiciously. Long-term complications of diabetes are very serious, diminish quality of life, and can take years off your life span. But long-term problems don't magically develop on their own, they happen slowly over time when daily care is mismanaged. This is one of the reasons why so many health care professionals are advocates of tight diabetes control.

Also, see "Diabetic Ketoacidosis."



What are normal glucose ranges?
American Diabetes Association Guidelines

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)
The following general guidelines for normal blood glucose ranges in nondiabetics* are from the American Diabetes Association. However, there are variations to these guidelines. For example, young children, those who are newly diagnosed, or are beginning insulin pump therapy may have slightly different target ranges.

Morning Fasting Blood Glucose

Fasting Glucose Ranges
Indication

From 70 to 99 mg/dL, or
3.9 to 5.5. mmol/L
Normal glucose tolerance, not diabetic

From 100 to 125 mg/dL, or
5.6 to 6.9 mmol/L
Impaired fasting glucose (IGF) or Pre-diabetes

126 mg/dL or higher, or
7.0 or higher
Diabetes



Normal and Target Blood Glucose Ranges in mg/dL for Diabetics

The American Diabetes Association sets certain guidelines for normal and abnormal blood glucose levels (appearing at the bottom of this article). However, as a person with diabetes, your doctor may set different ranges for you. Young children may have slightly higher target ranges than stable adults. And those starting out on insulin pump therapy or are newly diagnosed with diabetes may initially have higher target ranges to help avoid hypoglycemia during the initial phase of insulin pumping.

The following chart takes into consideration some of the possibilities that may alter target ranges. The ranges given are intended for general purposes only and not as a diagnostic tool, or, for you to change your own diabetes care plan. It is important that you know and understand the target ranges that your doctor sets specifically for managing your own diabetes.



Normal and Target Blood Glucose Ranges in mg/dL for Diabetics

Time of Day
Non-
Diabetic

Diabetic
Your doctor may set different ranges for you. USE THE TARGET RANGES YOUR
OWN DOCTOR SETS FOR YOU!
Notes for Diabetics Only
Your doctor will give you instructions tailored to your own medical needs.
BE SURE TO FOLLOW YOUR OWN DOCTOR's
PLAN DESIGNED FOR YOU!

Morning (Fasting) 70-99
90-130 (adults) 90-140 (children) Morning highs may be from the Dawn Effect or the Somogyi Effect.
Before Meals N/A
Typically:

90-130 adults & older children

100-140 children
"Before meals" means 2-4 hours after last meal was eaten. For those on rapid insulin only (pumps), generally by 2 hours you should be in, or close to, target range. Those on shot therapy may not be in range until about 4 hours after their last meal.
2-4 Hours After Meals 70-139
Less than 180 but high enough that hypoglycemia won't result from any "onboard" insulin if testing at only 1-2 hours. Pumpers typically come into target range faster than those on shot therapy (assuming both have given the correct amount of insulin). Ask your doctor when you should test (2 or 4 hours after a meal)

Before Bedtime N/A
Adults, usually 140-160

Children may have a higher pre-bedtime ranges than adults, up to 180
Have a pre-bedtime snack to help avoid nighttime lows. Note: high-fat snacks late in the evening can cause hyperglycemia (high BG) during the night.

Hypoglycemia(1)
(low blood glucose) 70 or lower
70 or lower

Newly diagnosed, and young children often have higher BG target for hypoglycemia (80-100); infants even higher.
Treat hypoglycemia anytime BG is 70 or lower. Newly diagnosed may be instructed to treat at 100. Stable, but young children may be advised to treat at 80-90. Bear in mind that 100 is fine 4 hours after eating but 100 would be too low only 1 hour after insulin. Be sure to ask your doctor WHEN (how long after insulin) to treat for hypoglycemia and not just by the BG reading alone.
Hyperglycemia
(high blood glucose) 200 or higher may indicate diabetes Over 180, 2-4 hours after a meal (2-4 for pumpers, 4 hours for those on shot therapy)

Over 140, morning fasting
Test urine for ketones when blood glucose is 240 or higher. Call doctor for care instructions when scheduled BG reading is over 240 more than twice in one day.

_____________________________
BG = blood glucose

(1) People that are newly diagnosed or just beginning a new type of therapy (such as insulin pumping or going from conventional insulin therapy to intensive insulin therapy) may have slightly higher target ranges set for a certain period of time. This is done to help avoid dangerous episodes of hypoglycemia (low blood glucose) while medication dose or method of delivery is being adjusted. Be sure to keep in close contact with your physician whenever your diabetes care plan changes.





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, and unfortunately, a part of diabetes that sometimes cannot be avoided. But long-term, excessive, or chronic high blood glucose levels can lead to many complications.

Short-term, reasonable, high blood glucose levels short-term (i.e., after meals) don't generally present 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 can damage organs and tissues throughout the body. Once this damage is done, serious life-long problems can occur.

Why worry about hyperglycemia? Isn't diabetes bad enough without having to deal with organ failure, amputation, and blindness (just some of the consequences of complications due to poor daily management)? And hyperglycemia increases the risks of all these and other diabetes complications.

Hyperglycemia can be attributed to multiple factors in diabetes as well as in nondiabetics. Let's examine some of those causes now.

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 Somogyi 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. The presence of excessive white fat reserves interferes with the body's ability to properly absorb and use insulin that is otherwise produced in sufficient quantity (see insulin resistance).

Chronic nondiabetic hyperglycemia can produce some of the same complications as diabetic hyperglycemia; however, some of the complications of diabetes mellitus (especially type 1) can occur even if blood glucose levels are kept under control, because the disease operates beyond just the condition of hyperglycemia.

Certain eating disorders can produce acute nondiabetic hyperglycemia, especially in the binge phase of bulimia nervosa when the subject consumes an incredible number of calories at once, frequently from foods that are high in carbohydrates and fats.

Other possible causes of elevated blood glucose include:

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

Causes of Hyperglycemia Related to Insulin Pump Use

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. On active days, many pumpers reduce their basal rates to compensate for the increase in exercise.

Another reason for 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.

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.

If you use an insulin pump, any time your blood glucose levels are high two readings in a row, you should change out the site and take an injection of insulin to correct the high. If this does not work, immediately call your doctor.

Your doctor can help you understand how to set basal rates, determine your insulin needs, and how to use "mini-fasts" on occasion to test your basal rates. For more information on insulin pumps and how to use them, see our "Diabetes Treatment" page.



Causes of 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 on 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 to help determine if you are chronically above target range.

People using insulin pumps, or other intensive therapy (sometimes also called flexible therapy) are required to test their blood glucose levels more frequently. Most persons on intensive therapy test 8-12 times per day and make adjustments via a correction bolus to bring down high blood glucose levels as soon as 2 hours after eating.

Other possibilities for hyperglycemia occurring while on shot therapy include:

Not getting all the insulin under the skin. If any leaks out, hyperglycemia may 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.



Hyperglycemia at Night

There are three main causes of hyperglycemia during the night:

Eating too much fat at dinner, or before bedtime
The Dawn Effect
Somogyi 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 in the brain. The Dawn Effect is also influenced by testosterone and tends to be more significant in men and in women with polycystic ovarian syndrome who may have elevated testosterone levels.

This resistance to insulin can cause you to need more insulin at certain times during the night. The Dawn Effect mildly occurs in nondiabetics as a means to elevated blood glucose to prepare for the day. In people without diabetes, the body adjusts so that blood glucose levels do not go too high. In those with diabetes, however, the Dawn Effect can cause blood glucose levels to rise too high and lead to morning fasting hypoglycemia.

Your overnight insulin is taken to counter the Dawn Effect, and on average, diabetics take 20% of their total daily insulin overnight due to an increase in metabolic needs during the night. People using 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.

Somogyi Effect (Rebound Hyperglycemia)

The Somogyi 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 the muscles and 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 termed "Somogyi Effect."

This may happen anytime during sleep, but hypoglycemia usually occurs around 3 a.m. The hypoglycemic (low blood glucose) episode is followed by an elevated is followed by an elevated blood glucose level towards morning. Going to bed without a snack or low blood-glucose, inadequate food eaten for exercise, and too much insulin contribute to this response.

Summary

The Dawn Effect is the early-morning increase in blood glucose, usually between 4 a.m. and 8 a.m. in persons with diabetes. The exact cause isn't known, however, it can be responsible for persistently elevated fasting blood glucose and HbA1c levels. It is not caused by a previous low during the night and treatment involves limiting fat in the diet at dinnertime and in bedtime snacks. Changes in insulin doses during the night are often required and should be made by your doctor.

The Somogyi Effect is triggered by low blood glucose that causes a release of hormones including glucagon that raise blood glucose too much. Low blood glucose occurs most often near an insulin peak so you may need to test your blood glucose levels more often for a few days to see where your lows are beginning.

To prevent or correct high blood glucose levels in the morning, your doctor may recommend:

Adjusting your dosage of medication or insulin
Switching to a different medication
Changing the time or fat content of your bedtime snack
Testing your blood glucose around 3.a.m.