This information explains high and low blood sugar and how to take insulin.


Just as a car needs gas to go, the body’s cells need sugar (glucose) to do their many tasks. Heart cells need sugar to pump blood and muscle cells need sugar to move. Insulin is a hormone that helps transport sugar from the blood into heart, muscle, and fat cells. Insulin is made by the pancreas. If the pancreas does not make enough insulin, blood sugar levels rise above normal. This happens because the sugar stays in the blood instead of going into the cells. This is called high blood sugar or hyperglycemia. It can occur if you:

  • Have Type 1 or Type 2 diabetes mellitus
  • Have had part or all of your pancreas removed
  • Take steroids like prednisone or Decadron®
  • Have a fever, an infection, or have had recent surgery

If diabetes medicines do not control your blood sugar levels, you will need insulin. You can take insulin only by injection. How much you take depends on:

  • Your blood glucose level
  • Your diet
  • Your activity level
  • Your overall health
  • Other medicines you take such as steroids

You can check your blood sugar level at home using a blood sugar meter. Your blood sugar target numbers are set by your doctor or diabetes educator. Targets will be set for fasting and for other times during the day. You should record all blood sugar results and insulin doses in a log book or on a paper record. This will be given to you by the doctor or nurse. Blood sugar monitoring:

  • Alerts you to high or low blood sugar (glucose) levels
  • Lets you know if you are within the target range
  • Helps you and your doctor decide how much insulin you need to bring your blood sugar within the target range

You will be in charge of controlling your blood sugar levels. You should:

  • Eat a healthy diet.
  • Increase your activity.
  • Check your blood sugar levels.
  • Take your diabetes medication or insulin as prescribed by your doctor or nurse.
  • See your doctor or nurse as directed.
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This happens when you have high blood sugar or a blood sugar above your target range. High blood sugar can cause many symptoms, such as:

  • Too much thirst or a dry mouth
  • A need to urinate often, especially at night
  • Hunger
  • Blurry vision
  • Drowsiness, fatigue, or tiredness
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This happens when you have low blood sugar or a blood sugar below 70. Low blood sugar can cause many symptoms, such as:

  • Sweating
  • Shakiness
  • Headaches
  • Feeling faint
  • A fast, forceful heartbeat
  • Weakness

If your blood sugar level is less than 70, follow the Rule of 15/15. The Rule of 15/15 is as follows:

  • Take 15 grams of sugar. This is equal to 4 ounces of juice, 8 ounces of milk, or 4 large glucose tablets. Do not eat chocolate or cookies.
  • Wait 15 minutes and retest your blood sugar.
  • If your blood sugar is still less than 70, take another 15 grams of sugar. Wait 15 minutes and retest. Do this until your blood sugar rises above 70.
  • When your blood sugar rises to 70 or more, eat half of a sandwich and drink 4 ounces of milk or juice, or you can have your scheduled meal instead.
  • Your insulin or diabetes medicine may need to be changed. Call your doctor or nurse to discuss this.
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Special Points

  • Stay on your healthy meal plan. Restrict the amount of sweet foods you eat.
  • Drink six to eight, 8-ounce glasses of water or diet, decaffeinated fluids each day. You should do this unless your doctor or nurse tells you not to.
  • Take your insulin or other diabetes medication as prescribed. Double-check the dose before you inject the insulin.
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Call Your Doctor Or Nurse If You:

  • Have a fever.
  • Have chills.
  • Have burning or pain when you urinate.
  • Take steroid medicines that are being tapered up or down or stopped.
  • Show signs of hypoglycemia or hyperglycemia that do not go away.
  • Have frequent hypoglycemia or hyperglycemia.
  • Have blood glucose readings of 400 mg/dl or more.
  • Have blood glucose readings of less than 70 mg/dl. First though, follow the simple rule for treating low blood sugar. When your blood sugar is back to 70 mg/dl or above, then you should call the doctor or nurse.

We recommend that you get a MedicAlert®ID. It should say that you have diabetes and the type of insulin you take. For more information, call 888-633-4298 or visit

Insulin Action Guide

Commonly used insulins at MSKCC







Aspart (Novolog)

5 - 15 min

30 to 60 min

3 - 4 hrs

Lispro (Humalog)

5 - 15 min

60 - 90 min

3 - 4 hrs


Novolin R Regular

30 - 60 min

2 - 5 hrs

6 - 8 hrs

Humulin R Regular

30 - 60 min

2 - 4 hrs

6 - 8 hrs


Novolin N (NPH)

1 to 2 hrs

6 - 12 hrs

12 - 14 hrs

Humulin N (NPH)

1 to 2 hrs

6 - 12 hrs

12 - 16 hrs



1 - 2 hrs

No peak

Up to 24 hrs

Detemir (Levemir
{1 to 2 injections daily}

1 - 2 hrs

No peak

Up to 24 hrs

Combination Fast and
Intermediate Acting

Novolog Mix 70/30 (N/Aspart)

30 min

1 - 12 hrs

5 - 18 hrs

Novolin 70/30 (N+R)

30 - 60 min

4 - 12 hrs

14 - 16 hrs

Humalog Mix 75/25 (N/Lispro)

5 - 15 min

1 - 12 hrs

14 - 18 hrs

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If you have any questions or concerns, talk with a member of your healthcare team. You can reach them Monday through Friday from 9:00 am to 5:00 pm at ____________________. After 5:00 pm, during the weekend, and on holidays, please call____________________. If there’s no number listed, or you’re not sure, call 212-639-2000.
©2015 Memorial Sloan Kettering Cancer Center - Generated on November 24, 2015