How Insulin Treatment Lowers Your Blood Sugar

Medically Reviewed by Michael Dansinger, MD on March 07, 2021

Insulin is a hormone your pancreas makes to lower blood glucose, or sugar. If you have diabetes, your pancreas either doesn't make enough insulin or your body doesn't respond well to it. Your body needs insulin to keep the blood sugar level in a healthy range.

How Diabetes Affects Insulin Production

Each diabetes type affects insulin production in a different way. Type 1 diabetes causes damage to the beta cells in your pancreas that make insulin. As a result, your body can't produce enough of this hormone. Type 2 diabetes gradually makes it harder for your beta cells to work, and also makes all the cells of your body less able to pull in and use insulin. 

In both types of diabetes, sugar from the foods you eat builds up in your blood. Constantly having high blood sugar damages your blood vessels. Over time, diabetes can cause problems with your nerves, eyes, kidneys, heart, and other organs.

Everyone with type 1 diabetes and some people with type 2 diabetes take a lab-made form of insulin to control their blood sugar.

How Insulin Treatment Helps Your Blood Sugar

Insulin treatment works in much the same way as natural insulin that the pancreas makes. After you eat, your body breaks down carbohydrates into glucose. That glucose goes into your bloodstream and causes your blood sugar level to rise.

When you take insulin, it helps to move glucose out of your bloodstream and into cells. Your cells use some of that sugar for energy and then store any leftover sugar in your fat, muscles, and liver for later.

Once the sugar moves into your cells, your blood glucose level should go back to normal.

How You Take Insulin

You can't take insulin as a pill because enzymes in your stomach would break it down during digestion. Instead, you inject insulin under your skin through a needle in a syringe, pump, or pen.

There is also a newer inhaled version of insulin. You breathe it in through a device that looks like an asthma inhaler.

People with type 1 diabetes need to take insulin several times a day. Those with type 2 diabetes may only have to take it once a day.

Types of Insulin

Insulin comes in four types. Each one starts to work at a different speed and controls blood sugar for a different amount of time:

Rapid-acting insulin starts to lower blood sugar within 15 minutes and its effects last for 2 to 4 hours.

Short-acting insulin starts to work within 30 minutes and its effects last for 3 to 6 hours.

Intermediate-acting insulin starts to work within 2 to 4 hours and lasts for 12 to 18 hours.

Long-acting insulin starts to work in a few hours and its effects last for 24 hours.

Show Sources


American Diabetes Association: "Insulin Basics."

Beyond Type 1: "Insulin delivery."

Diatribe: "Injected insulin."

Hormone Health Network: "What is Insulin?"

Mayo Clinic: "Diabetes: Diagnosis & treatment." "Diabetes: Symptoms & causes." "Diabetes treatment: Using insulin to manage blood sugar."

NIDDK: "Insulin, Medicines, & Other Diabetes Treatment."

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