Insulin is a hormone that your pancreas makes to allow cells to use glucose. When your body isn't making or using insulin the way it should, you can take manufactured insulin to help control your blood sugar.
Many forms of insulin treat diabetes. They're grouped by how fast they start to work and how long their effects last.
The types of insulin include:
- Rapid-acting, which starts to work within a few minutes and lasts a couple of hours
- Regular- or short-acting, which takes about 30 minutes to work fully and lasts 3 to 6 hours
- Intermediate-acting, which takes 2 to 4 hours to work fully. Its effects can last up to 18 hours.
- Long-acting, which can work for an entire day
- Pre-mixed
How Do I Take It?
Many people get insulin into their blood using a needle and syringe, a cartridge system, or pre-filled pen systems.
The place on the body where you give yourself the shot may matter. You'll absorb insulin the most evenly when you inject it into your belly. The next best places to inject it are your arms, thighs, and buttocks. Make it a habit to inject insulin at the same general area of your body, but change up the exact injection spot. This helps lessen scarring under the skin.
Inhaled insulin, insulin pumps, and a quick-acting insulin device are also available.
What Type of Insulin Is Best for My Diabetes?
Your doctor will work with you to prescribe the type of insulin that's best for you and your diabetes. Making that choice will depend on many things, including:
- How you respond to insulin. (How long it takes the body to absorb it and how long it remains active varies from person to person.)
- Lifestyle choices. The type of food you eat, how much alcohol you drink, or how much exercise you get will all affect how your body uses insulin.
- Your willingness to give yourself multiple injections per day
- How often you check your blood sugar
- Your age
- Your goals for managing your blood sugar
Your doctor may prescribe more than one type. You might need to take insulin more than once daily, to space your doses throughout the day, or to add other medicines.
Afrezza, a rapid-acting inhaled insulin, is FDA-approved for use before meals for both type 1 and type 2 diabetes. The drug peaks in your blood in about 15-20 minutes and it clears your body in 2-3 hours. It must be used along with long-acting insulin in people with type 1 diabetes.
The chart below lists the types of injectable insulin with details about onset (the length of time before insulin reaches the bloodstream and begins to lower blood sugar), peak (the time period when it best lowers blood sugar) and duration (how long insulin continues to work). These three things may vary. The final column offers some insight into the "coverage" provided by the different insulin types in relation to mealtime.
| Type of Insulin & Brand Names | Onset | Peak | Duration | Role in Blood Sugar Management |
| Rapid-Acting | ||||
| Lispro (Humalog) | 15-30 min. | 30-90 min | 3-5 hours | Rapid-acting insulin covers insulin needs for meals eaten at the same time as the injection. This type of insulin is often used with longer-acting insulin. |
| Aspart (Novolog) | 10-20 min. | 40-50 min. | 3-5 hours | |
| Glulisine (Apidra) | 20-30 min. | 30-90 min. | 1-2 1/2 hours | |
| Short-Acting | ||||
| Regular (R) or novolin | 30 min. -1 hour | 2-5 hours | 5-8 hours | Short-acting insulin covers insulin needs for meals eaten within 30-60 minutes. |
| Velosulin (for use in the insulin pump) | 30 min.-1 hour | 1-2 hours | 2-3 hours | |
| Intermediate-Acting | ||||
| NPH (N) | 1-2 hours | 4-12 hours | 18-24 hours | Intermediate-acting insulin covers insulin needs for about half the day or overnight. This type of insulin is often combined with a rapid- or short-acting type. |
| Long-Acting | ||||
| Insulin glargine (Basaglar, Lantus, Toujeo) | 1-1 1/2 hours | No peak time. Insulin is delivered at a steady level. | 20-24 hours | Long-acting insulin covers insulin needs for about one full day. This type is often combined, when needed, with rapid- or short-acting insulin. |
| Insulin detemir (Levemir) | 1-2 hours | 6-8 hours | Up to 24 hours | |
| Insulin degludec (Tresiba) | 30-90 min. | No peak time | 42 hours | |
| Pre-Mixed* | ||||
| Humulin 70/30 | 30 min. | 2-4 hours | 14-24 hours | These products are generally taken two or three times a day before mealtime. |
| Novolin 70/30 | 30 min. | 2-12 hours | Up to 24 hours | |
| Novolog 70/30 | 10-20 min. | 1-4 hours | Up to 24 hours | |
| Humulin 50/50 | 30 min. | 2-5 hours | 18-24 hours | |
| Humalog mix 75/25 | 15 min. | 30 min.-2 1/2 hours | 16-20 hours | |
| *Premixed insulins combine specific amounts of intermediate-acting and short-acting insulin in one bottle or insulin pen. (The numbers following the brand name indicate the percentage of each type of insulin.) | ||||
How Are Doses Scheduled?
Follow your doctor's guidelines on when to take your insulin. The time span between your shot and meals may vary depending on the type you use.
In general, though, you should coordinate your injection with a meal. You want to time your shot so that the glucose from your food gets into your system at about the same time that the insulin starts to work. This will help your body use the glucose and avoid low blood sugar reactions. From the chart on page 1, the "onset" column shows when the insulin will begin to work in your body. You want that to happen at the same time you're absorbing food. Good timing will help you avoid low blood sugar levels.
- Rapid acting insulins: About 15 minutes before mealtime
- Short-acting insulins: 30 to 60 minutes before a meal
- Intermediate-acting insulins: Up to 1 hour prior to a meal
- Pre-mixed insulins: Depending on the product, between 10 minutes or 30 to 45 minutes before mealtime
Exceptions to Insulin Dosing and Timing
Long-acting insulins aren’t tied to mealtimes. You’ll take detemir (Levemir) once or twice a day no matter when you eat. And you’ll take glargine (Basaglar, Lantus, Toujeo) once a day, always at the same time. Deglutec is taken once a day, and the time of day can be flexible. But some people do have to pair a long-acting insulin with a shorter-acting type or another medication that does have to be taken at meal time.
Rapid-acting products can also be taken right after you eat, rather than 15 minutes before mealtime. You can take some of them at bedtime.
For more information about when to take insulin, read the "dosing and administration" section of the insulin product package insert that came with your insulin product, or talk with your doctor.
Insulin Side Effects
The major ones include:
- Low blood sugar
- Weight gain when you first start using it
- Lumps or scars where you've had too many injections
- Rash at the site of injection or, rarely, over your entire body
With inhaled insulin, there's a chance that your lungs could tighten suddenly if you have asthma or the lung disease COPD.
Storing Injectable Insulin
Always have two bottles of each type you use on hand. You don't need to refrigerate vials of insulin that you're using. A good rule of thumb is that if the temperature is comfortable for you, the insulin is safe. You can store the bottle that you're using at room temperature (not higher than 80 F) for 30 days. You don't want it to get too hot or too cold, and keep it out of direct sunlight.
Keep your extra backup bottles in the refrigerator. The night before you're going to start using a new bottle, take it out and let it warm up. Don't let your insulin freeze.
Always look at your insulin inside the bottle before you draw it into the syringe. Rapid-acting, short-acting, and certain long-acting types should be clear. Other forms may look cloudy, but they shouldn't have clumps.
If you carry a bottle with you, be careful not to shake it. That makes air bubbles, which can change the amount of insulin you get when you withdraw it for an injection.
For insulin pens, check the package insert for storage instructions
Storing Inhaled Insulin
Check the directions on the package. You should keep a sealed package in the refrigerator until you're ready to start using it. If you don't, you must use it within 10 days.
You can refrigerate packages you've opened, but let a cartridge warm up to room temperature for 10 minutes before you use it.