Aug 1, 2004 Table of Contents

Please note: This information was current at the time of publication. But medical information is always changing, and some information given here may be out of date. For regularly updated information on a variety of health topics, please visit familydoctor.org, the AAFP patient education Web site.

Information from Your Family Doctor

Your Insulin Therapy

Am Fam Physician. 2004 Aug 1;70(3):511-512.

Your doctor has given you insulin to help control your diabetes. You need two kinds of insulin: basal and mealtime insulin. Sometimes insulin is premixed for you. Keep a record of your blood sugar and insulin shots every day so the amounts of insulin can be changed to fit your lifestyle.

Your basal insulin type and dose are (your doctor will fill in the blanks):

  • NPH insulin: Inject _____ units at ____ a.m. and _____ units at _____ p.m.

  • Ultralente or glargine (Lantus): inject ____ units at _______ a.m./p.m.

    • Basal insulin provides steady levels of insulin. NPH lasts 10 to 16 hours. Ultralente and glargine last 24 hours.

    • Take your basal insulin at the same time every day.

    • Do not skip your basal insulin shots, even if you are sick. Your body still needs the basal insulin.

    • Do not mix glargine with other insulins. NPH can be mixed.

    • Do not take glargine if you are pregnant or planning to become pregnant.

    • Your basal insulin dose should be increased every seven days until your fasting blood sugar level is between 90 and 130 mg per dL. Talk to your doctor about how much to increase your dose.

Low blood sugar (this is called hypoglycemia) can happen if you take too much insulin.

  • Symptoms of low blood sugar include shakiness, weakness, dizziness, confusion, and headache. Some people may not have symptoms.

  • Check your blood sugar level if you have any of these symptoms. You also should check your blood sugar level during your insulin's peak of activity (talk to your doctor about this).

  • If your blood sugar level is below 70 mg per dL, follow the Rule of 15:

    1. Eat or drink 15 grams of carbohydrates (e.g., one half glass of orange juice or one slice of bread).

    2. Wait 15 minutes, and test your blood sugar level again.

    3. If your blood sugar level is still below 70 mg per dL, do steps 1 and 2 again. If your blood sugar level now is above 70 mg per dL, go back to your usual testing schedule.

  • Your risk of low blood sugar depends on the kind of insulin you use and how long it works. Aspart and lispro last 4 hours, regular insulin lasts 6 hours, NPH lasts 10 to 16 hours, and glargine and ultralente last 24 hours.

  • If you have trouble getting your blood sugar level back above 70 mg per dL, call your doctor or local emergency room for help.

Your mealtime insulin type and dose are (your doctor will fill in the blanks):

  • Regular insulin: Inject it 30 to 60 minutes before you eat.

  • Lispro (Humalog) or aspart (NovoLog): Inject it 5 to 15 minutes before you eat.

How much insulin you use before meals changes from meal to meal. Spell the word “SAFE” to figure out how much insulin you will need at mealtime:

Supplemental insulin—supplemental, or corrective, insulin will get your blood sugar level back into the range of 90 to 130 mg per dL before meals. Test your blood sugar level before the meal (if your blood sugar level is below 70 mg per dL between meals, follow the Rule of 15). Use the table below to find how much you need to change your insulin dose. One unit of insulin should cause your blood sugar level to drop 30 to 50 mg per dL, but you may need more insulin to get the same effect.

Blood sugar level Supplemental insulin dose

Higher than 200 mg per dL

Add 2 units of insulin

150 to 200 mg per dL

Add 1 unit of insulin

100 to 149 mg per dl

No change

70 to 100 mg per dL

Subtract 1 unit of insulin

Below 70 mg per dL

Subtract 2 units of insulin

Blood sugar level Supplemental insulin dose

Higher than 200 mg per dL

Add 2 units of insulin

150 to 200 mg per dL

Add 1 unit of insulin

100 to 149 mg per dl

No change

70 to 100 mg per dL

Subtract 1 unit of insulin

Below 70 mg per dL

Subtract 2 units of insulin

Activity—take _______ units less insulin if you plan to exercise after the meal.

Food—carbohydrates; take 1 unit of insulin for every 10 grams of carbohydrate in your meal. A typical meal has 45 to 60 grams of carbohydrates, so you will need to take about 4 to 6 units of insulin per meal. People with insulin resistance may need to take more insulin to get the same effect.

Experience—You will learn how much insulin you need at different times. Keep a record of your blood sugar levels and the amount of insulin you take every time. This will help you remember what has worked for you in the past. Bring this record with you every time you see your doctor.

SAFE total: _____ This is the amount of mealtime insulin you should inject.


This handout is provided to you by your family doctor and the American Academy of Family Physicians. Other health-related information is available from the AAFP online at http://familydoctor.org.

This information provides a general overview and may not apply to everyone. Talk to your family doctor to find out if this information applies to you and to get more information on this subject.

Copyright © 2004 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact afpserv@aafp.org for copyright questions and/or permission requests.

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