Effect of Food and Insulin on Blood Sugars

Learn how food and different types of insulin (long acting and fast acting, or lantus and bolus insulin) affect your blood sugars.


Effect of Food and Insulin on Blood Sugars

Megan Robinson, MS, RD, CDE, LDN: How does insulin and food affect your blood sugar? You’re taking two types of insulin. Lantus or Levemir insulin you can see in green is your basal insulin, also known as your long-acting insulin. And Novolog, Humalog or Apidra insulin you can see in blue is your bolus insulin, also known as your fast-acting. Let’s talk about your basal insulin first.

Lantus or Levemir insulin is typically given around the same time at night and can last up to 24 hours. Since Lantus is a basal insulin, it keeps your blood sugars within range between meals and while you are sleeping. It does not work on foods like carbohydrates. Your Bolus insulin, or in other words, your Novolog, Humalog or Apidra, you can see in blue, is a fast-acting insulin. These types of insulin begin working quickly, within 10 to 20 minute, peaks or works the hardest in two hours, and wears off in three to four hours.

This may vary from person to person. Fast-acting insulin has two functions — to lower high blood sugars and to cover carbohydrate grams. Every time you eat carbohydrates, you should give yourself fast-acting insulin to keep your blood sugars within a healthy range.

Carbohydrate foods you can see in red, such as seen in fruits, milk, grains and sweets, break down to glucose or blood sugar quickly in your body. When you eat a food containing carbohydrates, it begins to raise your blood sugar within 10 minutes, can peak 60 to 90 minutes after eating. And, if you take the correct amount of fast-acting insulin to cover the carbohydrate grams in your meal and count your carbohydrates correctly, your blood sugar should lower to a healthy range within three hours.

It is important to remember that most kids need to take fast-acting insulin before they eat meals or snacks to allow the insulin to work with the carbohydrates to help lower your blood sugar. Younger kids may post dose or give insulin after they eat. Keep in mind though, you should finish eating your meals or snack in less than 30 minutes to make sure that the insulin and the carbohydrates are working together to keep your blood sugars healthy.

Topics Covered: Type 1 Diabetes, Type 2 Diabetes, Cystic Fibrosis-related Diabetes

Related Centers and Programs: Diabetes Center