High Blood Sugars (Hyperglycemia)

High blood sugar, also known as hyperglycemia, can leave you feeling tired, thirsty, irritable, hungry, and unable to concentrate. What’s worse is that these high blood sugars can lead to complications like kidney and eye damage, nerve damage, even blindness, and foot amputations over time.

Occasionally, you can bring down high blood sugar by drinking lots of water, walking, or taking a correction dose of insulin. On the other hand, chronically elevated high blood sugar should be evaluated—what are the reasons, and what actions can you take to prevent those highs from happening in the first place?

Your A1c number can help you see if you are chronically high.

For those with Type 1 diabetes, there is almost always one cause: not enough insulin. You may need to decrease your carb ratio, change your correction factor, adjust your basal insulin, and analyze your Total Daily Dose. Talk to your doctor or diabetic educator or look at our tools if you need help. If you’re on a pump and CGM, see our Insulin Dose Guide for Pumps, CGMs, and AIDs.

In Type 2, increased exercise and better food choices, adding or adjusting medication, or adding insulin to your treatment plan may be the answer.

In all types of diabetes, when blood sugars are very high, a dangerous state of acidification of the blood can occur, known as Ketoacidosis or DKA. If your blood sugar is 250 or higher, check for urine ketones using ketone test strips. If ketones at moderate or large levels, nausea, vomiting, or rapid breathing are present, call your physician or go to the ER immediately. Look here for more information about recognizing and treating DKA [link to new DKA page].

To prevent chronic but not dangerously high blood sugars, read on.

How To Prevent Highs

For better blood sugars and fewer lows, test often and review your readings once a week for patterns of lows or highs, or both. Identify these problems, then consider their causes and how to correct them. Make one change at a time and correct lows first. If you need any advice at all about how to correct a problem, be sure to call your physician or nurse educator right away. Do not let control problems linger as they usually turn into larger problems.

When trying to prevent high blood sugars, it helps to understand their most common causes. The table below outlines the most common causes. If you are currently experiencing either frequent or severe reactions, look carefully at this list to see what is causing them.

Common Triggers And Corrections
Too Many Highs*
Cause Correction
too little insulin more insulin
more eating less eating or more insulin
weight gain less weight or more insulin
high fat diet less fat or more insulin
less exercise more exercise or more insulin
Sudden Highs*
Cause Correction
infection, cold, flu, or illness more insulin until over
excess food less food or more insulin
missed insulin take insulin
insulin left in hot car,frozen,out of date use new insulin
stress manage stress
pain pain medication or more insulin
premenstrual more insulin at this time
prednisone, cortisone more insulin while on Rx

* If your blood sugar is 250 or higher, check for urine ketones. If ketones are present at moderate or large levels, call your physician immediately.

Daily Highs
Highs Between Meals
Cause: Choose one correction:
Food and insulin are not matched Inject earlier before the meal
Eat a smaller meal, add a snack later
Add fiber (psyllium or guar gum)
Eat foods with a lower glycemic index
Highs Before Breakfast
Cause: Choose one correction:
Mismatch between overnight insulin and insulin need Add more evening NPH or Lente
Move dinner NPH/Lente to bedtime, especially if you have had nighttime lows in the past.
Start to exercise in the evening
Stop low blood sugars at bedtime
Use an insulin pump
Highs Before Lunch
Cause: Correction:
Too little breakfast H, N or R, too much breakfast carbs, night reactions Add more H, N or R for break-
fast, rule out nighttime lows by testing
at 2 a.m.
Highs Before Dinner
Cause: Correction:
Too little lunch H/N/R, too little
breakfast L/NPH/UL, excess lunch carbs
Add more H, N or R at lunch,
long-acting insulin at breakfast, or fewer
carbs at lunch
Variable Blood Sugars
Cause: Choose one correction:
Frequent or severe low blood sugars Regulate your lifestyle, exercise, and stress for a more recognizable pattern to your charts; less insulin is often needed.


Discuss with your physician an insulin regimen more adapted to your lifestyle.

Erratic eating (different amounts, different times)
Skipped meals
Insulin doses change a lot each day
Exercise that varies in time, length, or intensity
No exercise at all
Irregular sleep hours

Pumping Insulin provides much more pump information and is the most helpful book ever written on insulin use.

Using Insulin takes you step-by-step toward excellent control. Whether you use one injection and pills, or six injections, you’ll learn far more from this book than from any other!