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What You Should Know About Insulin

Middle aged man with glasses, smiling.Insulin is a hormone made by the pancreas. It helps lower your blood sugar by moving sugar from the blood into the cells of your body. Once inside the cells, sugar provides energy. If your body doesn't make enough insulin, you may have to get the insulin by shots (injections) using a small, short needle that goes just under the skin into the fat.

There are different kinds of insulin. The difference in them is how fast they start working to lower your blood sugar, how long they last, and when the activity is the strongest. How fast insulin works depends on:

  • Your own response
  • The place on your body where you give your insulin shot
  • The type and amount of exercise you do
  • The length of time between your shot and exercise

Insulin is measured in units. Insulin comes in different strengths. Most insulins in the US have 100 Units of insulin for each cc (cubic centimeter) of fluid. It is called U-100 strength.

There are special syringes for insulin. The markings are in "units". They come in 4 different sizes: 25 units, 30 units, 50 units, or 100 units. It is not unusual for people to take 3 or more shots per day. The dose is based on your blood sugar test results. Remember, just because you take more insulin does NOT mean your diabetes is worse.

The key to success is developing, with your health care team, a plan for the insulin shots that fits your lifestyle.

What To Do

Insulin is given in the fat layer beneath the skin on four general areas of the body: the back of the arms, the top or outer side of the upper legs (not on the inside), the buttocks, and the stomach. Each shot should be given in a different spot. Talk with your health care provider/diabetes educator to figure out a plan.

Where the shot is and how deep affects how fast it acts. When you give the shot, pinch the skin up gently. Stick the needle straight in quickly. Slowly push the insulin in. If you give the shot in your abdomen, you should stay at least 1-2 inches from your belly button. That's about 2 finger widths. The shot should be at least 1 inch from the previous site or 1-2 finger widths away.

It is important to draw up the exact amount you are supposed to take. Before you draw up the insulin you should check to see that the fact-acting insulin or the long-acting Lantus® looks clear. Long acting insulins (except Lantus®) look cloudy, but you should not see any floating lumps or changes in color. You should also check the expiration date. Throw away insulin that doesn't look like it's supposed to or if it has expired.

Insulin can be stored at room temperature for 30 days as long as the temperature is less than 86 degrees. When you open a new bottle, write the date that is 30 days away on it. That is when you should throw it away.

If you get several bottles at once, keep the unopened bottles in the refrigerator. Do NOT freeze. Treat the bottles of insulin gently. Keep away from heat and sunlight. If it is very hot, you should keep all of the insulin in the refrigerator and warm the bottle by holding it in your hand for a few minutes before drawing it up. Or, once you draw up the insulin, roll the syringe gently between your hands until it feels warm. (Warm insulin hurts less than cold when given.) Before you draw up medium and long acting insulin (the cloudy ones) you should roll the bottle between the palms of your hands for about 20 times or tip it up and down about 10 times gently. Do not shake.

Your diabetes nurse educator is the key to learning:

  • how to draw up insulin
  • how to give insulin shots
  • special precautions when traveling

You should contact your health care provider often when you start on insulin.

Types of Insulin
Type Begins Working Works Hardest (peaks) Stops Working Comments
(Humalog®, Humulin®)
Very Short acting
10-15 min. 30-90 min. 4-5 hours Should be taken just before eating. Looks clear in bottle. When combining Humalog and Regular, it doesn't matter which one is drawn up first. It should be drawn up before NPH or ultralente.
Very Short acting
10-15 min. 40-50 min. 3-5 hours Should be taken just before eating (within 5-10 minutes). Looks clear and colorless in bottle.
Short acting
30-60 min. 2-4 hours 6-9 hours Given near mealtime (about 30 minutes before eating). Looks clear in bottle. When combining Regular and Humalog, it doesn't matter which one is drawn up first. It should be drawn up before NPH or ultralente.
Moderate acting
2-4 hours 4-8 hours 12-16 hours Usually taken in the morning or before bed. Looks cloudy in bottle. There should be no lumps.
Slow acting
4-8 hours 6-12 hours 15-20 hours Mixing ultralente and Humalog does not slow the activity of the Humalog. Mixing ultralente and Regular slightly slows the onset of activity in the Regular.
(Insulin Glargine)
2-4 hours 4-24 hours up to 24 hours Do not mix with other insulins. Looks clear.

There are also premixed insulins that combine shorter acting insulins with longer acting insulins.


Insulin lowers your blood sugar whether you eat or not. You should eat on time if you take insulin. The insulin you take and the food you eat must be balanced. Do not skip meals. Otherwise you can develop low blood sugar. Low blood sugar needs to be treated right away so that you don't pass out.

Usually insulin given in the belly is absorbed the fastest. If you will be doing exercise using the arm(s) or the leg(s), it is better to give the insulin in an area not directly being exercised. Otherwise, the insulin will be used faster. For example, if you are playing tennis, don't inject the arm that you swing the racquet with. It is better to not take insulin just before a warm bath or shower since the warmth will cause the insulin to be absorbed faster.

Insulin pens are available. With a pen you don't have to draw up the insulin. You simply dial the amount you want and give yourself the shot.

After you have been giving yourself shots for a while, you may want to learn more about pumps. Using a pump requires very careful balance between the food you eat, testing your blood sugar, and giving yourself insulin. If you think this is something you might like, talk to your diabetes educator or health care provider.

Insulin can cause weight gain.



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Exercise - Staying Healthy: Things To Do - Measuring Your Blood Sugar - High & Low Blood Sugar Diabetes Pills - Insulin - Sick Days - Foot Care - Resources - Home Page

This guide is not a substitute for the judgment of trained professionals.
If you are a person with diabetes you should seek care from a qualified practitioner.