Mealtime insulin is a fast-acting insulin type. A doctor may prescribe it alongside longer-acting insulin types to help manage blood glucose levels while living with diabetes.

When you live with diabetes, you may need to use medications to manage your condition. Sometimes, a doctor may prescribe you insulin to manage your blood glucose levels. Depending on your condition, a doctor may use one or more types of insulin to keep your blood glucose level within a “normal” range.

For example, mealtime insulin types are fast-acting. They’re taken immediately before meals to help control blood glucose spikes that happen when you eat. A doctor may prescribe mealtime insulin to take on top of long-acting insulin, which helps to keep your blood glucose level stable in between meals.

The amount and type of insulin varies from person to person. This depends on diet, lifestyle, and your particular case.

Read on to learn more about mealtime insulin, including how it differs from other types of insulin and the best way to take it.

Mealtime insulin works differently from how other types of insulin work. The major difference between the different types of insulin is how quickly they start acting in the blood (onset), when they’re at their peak strength (peak time), and how long they’re effective (duration). Here’s a breakdown:

  • Rapid-acting (mealtime) insulin, sometimes called bolus insulin, is designed to quickly act on blood glucose during a meal. The effects of this type of insulin can start within 15 minutes and peak after about 1 to 2 hours. It works for roughly 3 hours.
  • Regular (short-acting) insulin begins to work 30 minutes after injection, peaks between 2 and 3 hours after the injection, and works for between 3 and 6 hours.
  • Long-acting insulin, also called basal or background insulin, works in your body throughout the day to control your blood glucose, even when you’re not eating. The effects usually start a few hours after injection and last up to 24 hours.
  • Intermediate-acting insulin is similar to long-acting insulin, except it doesn’t work for quite as long. It reaches the bloodstream from 2 to 4 hours after injection and is effective for about 12 to 18 hours.
  • Ultra-long-acting insulin comes into effect in 6 hours. Because it doesn’t peak, it can last for more than 36 hours.

The biggest benefit of taking mealtime insulin on top of a long-acting or intermediate regimen is that it allows you to closely match how your own body would naturally release insulin if it was able to do so.

Another advantage is that it allows your mealtimes to be flexible. As long as you remember to take your mealtime insulin 15 to 20 minutes before your meal or snack, you can eat your meals whenever you’d like.

Many doctors will start you on long-acting insulin at first. But sometimes long-acting insulin isn’t enough to keep your blood glucose at your target level throughout the day.

When you eat a meal, glucose levels in the blood can rise rapidly. This “spike” in blood glucose may be too high for long-acting insulin to control. This is when a doctor may want to add mealtime insulin to your long-acting therapy or prescribe combination insulin.

A doctor will work with you to figure out if you need mealtime insulin. They’ll have you take note of how much your blood glucose fluctuates throughout the day. They’ll also ask about your lifestyle and eating habits.

A doctor will likely recommend that you add mealtime insulin to your long-acting insulin if your glucose levels are still too high after eating a meal.

You’ll continue to take your long-acting insulin as prescribed by a doctor. But you’ll also take the mealtime insulin right before you eat your meals (such as right before breakfast, lunch, dinner, or a large snack).

As the name suggests, mealtime insulin is taken at mealtimes, usually right before a meal.

Before you inject mealtime insulin, you’ll have to determine how much insulin you need. The amount you take depends on how many carbohydrates you plan on eating in your meal.

The higher the amount of carbohydrates a food contains, the more that food will raise your blood glucose. This means you’ll need more insulin. You’ll also need to be mindful of carbohydrate totals in your meals and snacks.

Note that carbs aren’t the only factor that can affect blood glucose levels. Activity levels, alcohol, medications, menstruation, and other factors can also contribute.

If you’re not sure how to calculate the amount of insulin you need based on the amount of carbohydrates you have with your meals and snacks, ask a doctor, registered dietitian, or certified diabetes educator. There are also several smartphone apps available to supplement their guidance.

In addition to your diet, your level of exercise and general activity also influences how much insulin you need to inject at mealtimes. Exercise can increase sensitivity to insulin for 72 hours or longer. This means you may require a reduction in insulin doses.

Insulin shots work best when injected in areas with higher fat content, such as your abdomen, and when the injection spots are rotated to prevent lipohypertrophy, or a mass of accumulated fat at the injection site.

When you begin taking insulin, a doctor might check in with you often. They may have you tweak the amount you take or the time you take it based on the results of blood tests. You may need to fine-tune your dose and schedule until you find the ones that work best.

Research shows that the best time to take mealtime insulin is 15 to 20 minutes before you eat a meal. Taking mealtime insulin after your meals may put you at a greater risk of low blood glucose, or hypoglycemia.

However, don’t panic if you forget to take your insulin before your meal.Instead, take it at the end of the meal and keep an eye on your blood glucose.

If you forget to take your insulin and it’s already time for another meal, your blood glucose level will probably be higher than it normally is before a meal. If this happens, measure your blood glucose and then adjust for the meal, adding a correction dose to cover the higher glucose level. Talk with a doctor or a certified diabetes educator about how to use a correction dose to manage elevated blood sugars when you miss a dose.

If you forget to take your mealtime insulin often, talk with a doctor or certified diabetes educator. They may prescribe a different type of insulin for you.

One disadvantage of mealtime insulin is the need to inject yourself with insulin multiple times per day. Talk with a doctor for guidance if this is a challenge in any way. They can help with ways to reduce any discomfort caused by insulin injections.

Mealtime insulin also requires you to keep note of your carbohydrates and adjust your dosage accordingly. This can take a fair amount of patience and practice. A doctor and diabetes care team can give you guidance on how much insulin to take.

Blood glucose testing will be useful to help you learn how much insulin you need to take. One side effect of mealtime insulin is potential weight gain. Unplanned weight gain while taking insulin can be managed by working with a healthcare team, such as a doctor, registered dietitian, and exercise physiologist, to come up with a meal and an exercise plan that fit with your lifestyle, ability, and health goals.

Mealtime insulin also comes with other risks. If you take your mealtime insulin but are unable to eat, you could become hypoglycemic, which occurs when your blood glucose levels get too low and can have serious side effects. When your blood glucose is too low, you may feel tired, weak, irritable, and more.

To stop the effects of hypoglycemia, use the “15-15 rule” to manage low blood glucose. In other words, have 15 grams of carbohydrates to increase your blood glucose level and check your levels again after 15 minutes.

Here are some examples of medications and foods that can provide you with 15 grams of carbohydrates when you’re experiencing hypoglycemia:

  • glucose tablets (read the instructions)
  • 1/2 cup (4 ounces) of fruit juice or regular soda (not diet soda)
  • 1 tablespoon of table sugar, honey, or corn syrup
  • hard candies such as LifeSavers (check the nutrition facts panel to see how many grams of carbohydrates they provide)

If your blood glucose level is still under 70 milligrams (mg) per deciliter (dL), repeat the 15-15 rule until your blood glucose is above this level. After it reaches above 70 mg/dL, eat a meal or a snack to keep your blood glucose level within your typical “normal” range.

When used together with a long- or intermediate-acting insulin, mealtime insulin is a great way to mimic your body’s natural insulin schedule. It may take a bit of practice to understand how much mealtime insulin you need before you eat a meal or snack, but you’ll eventually learn what’s best for your body.

If you’re not sure how often to inject mealtime insulin, how much to inject, or how to measure your blood glucose, ask a doctor or certified diabetes educator. Always check with them before changing your dose or typical routine.