Does Insulin Make You Gain Weight?

People with Type 2 diabetes are often treated using insulins but did you know that weight gain is a common side effect? Insulins help the body absorb blood sugar for energy but if isn’t used, we store that energy as fat. In this article, we explain how insulins can lead to weight gain and give you practical tips for maintaining a healthy weight.

Insulin and Type 2 Diabetes

Type 2 diabetes is a condition where blood sugar exceeds normal or healthy levels. It’s commonly due to inadequate insulin production because the pancreas has been overworked after years of high blood glucose levels. It can also be from insulin resistance, where the cells aren’t able to use insulin effectively.

Insulin is a vital hormone released by the pancreas and absorbs blood glucose into cells. But when there isn’t enough insulin, glucose stays in the blood and over time leads to disorders and complications.

How Insulin is Made

Researchers Frederick Banting and Charles Best (Source:

The history of injected insulin actually dates back over 100 years. Researchers Frederick Banting and Charles Best in 1921 discovered how to extract and refine insulin from the pancreas of animals, and was first successfully used on a human in 1922. It wasn’t until the 1980s that an engineered, synthetic insulin was made that didn’t depend on animals (called “human insulin”).

Today, human insulin is made mostly from common bacteria. The processes may differ but generally the bacteria is used to create a protein, which is then modified to create the human protein that produces insulin.

Because insulin contains proteins, exposure to extreme heat or cold can damage or spoil insulin. In this case the insulin will not be as effective in lowering blood sugar levels. So consider using a portable insulin cooler when traveling or being out for several hours.

Insulin Therapy

Insulin is one of the most common treatments for people with Type 2 diabetes, second only to Metformin. Because the body can’t produce enough or use it efficiently, insulin therapy is used to help the body control blood sugar levels.

Insulin and Weight Gain

Weight gain is a common side effect when people with type 2 diabetes start using insulin. Insulin’s function is to absorb glucose from the blood, which is then used for energy or stored in muscles or the liver.

But if the body doesn’t use that glucose for energy, it stays in the muscles and becomes fat. And as that fat builds up, this leads to the weight gain that people may experience.

Still… Insulin Has a lot of Benefits

While some people may gain weight, insulin offers a lot of benefits in treating people with diabetes and is why it continues to be an important part of diabetes self care.

Long History of Use

As mentioned above, insulin has a long history and was first used to treat people a 100 years ago. So there’s plenty of research showing its safety and effectiveness in helping control blood sugar.

Natural Hormone Replacement

Taking insulin is a more natural treatment option than other diabetes medications. You’re basically replacing the hormones your body would have created anyway, while most medications include substances that are new to your body.

Of course always discuss your treatment plan with your care provider but some people may prefer more natural treatment options.

Easily Adjustable to Meet Needs

Insulin doses can be easily adjusted to better meet glucose targets or address a patient’s needs. Common diabetes medications – like Metformin, Victoza or Jardiance – tend to have fixed dosing which can make any adjustments more limited.

But insulin doses can be adjusted to any amount. And you can make adjustments between each dose. For example, you may need to increase a dose before a large, higher carb lunch but then take lower dose a few hours later before a light dinner.


Nowadays, you can take insulin using a syringe, reusable or disposable insulin pens, or even through inhalers! Having different delivery methods gives you options to make taking insulin more convenient during your day.

insulin pen
SoloStar insulin pen made by Lantus

How to Control Weight Gain on Insulin

Fortunately, you can do different things to have less weight gain. And most of these may already be part of your diabetes self care.

Adjust Insulin Dosage

There’s two types of insulin used: basal and bolus. Basal is long-acting and keeps blood glucose levels steady throughout the day. Bolus is fast-acting and is meant to prevent blood sugar spikes and is taken before meals (why they’re also called “mealtime insulin”).

Many people with Type 2 diabetes are prescribed both basal and bolus insulins. So if you start gaining bodyweight, speak with your care provider about possibly adjusting the basal and bolus dosages.

Often times the total daily basal dosage may be too high in relation to a person’s weight and creates an imbalance with the bolus dosage. This causes glucose absorption throughout day, which increases chances of having unused glucose turn into fat.

Instead, your care provider can lower the basal dosage while also increasing the bolus dosage. This will help focus glucose absorption around meal times when blood sugar is more likely to spike and help with not leading to as much weight gain.

Watch Your Calorie Intake

Whether you’re on insulin or not, gaining weight happens when the calories you consume are higher than the calories you use for energy. So you’ll want to make sure your calorie intake is close to your physical activity level.

One way is to count calories of your meals but this takes a lot of time and effort for most people. Instead, a simpler way is to control portion sizes using the diabetes plate method. You take a 9″ plate and fill with 50% non-starchy vegetables, 25% protein and 25% carbs. This offers a more balanced meal where you’re less likely to overeat.

plate method for diabetes
Also, Watch Your Carbohydrate Intake

Limiting carbs is already a part of diabetes self care but they also play a role in weight gain. Breads, crackers and sugary fruit are common “go to” snacks but if you’re not careful, those calories can add up quickly.

It’s better to eat carbs as part of a meal and try to limit up to 30 grams per serving. And if you have carbs for snacks, avoid carbs from refined processed foods because they often cause blood sugar spikes.

Staying Active

Regular exercise and physical activity burns calories, which helps lower glucose but also helps prevent weight gain. And a combination of cardio and resistance training is ideal for people with type 2 diabetes.

Cardio exercises not only burns calories but also improves blood pressure, resting heart rate, and overall heart health. Heart disease is a often associated with Type 2 diabetes and is a serious health condition that should be addressed. Brisk walking, light jogging or bike riding are good options because they’re light intensity and can be done at your own pace.

woman walking for exercise

Resistance training can burn a lot of calories and helps the body add muscles. Weight lifting or using resistance bands to train multiple muscles can burn more calories in a shorter amount of time than cardio.

And adding muscles is not just for looks. Muscles absorb glucose to help lower blood sugar levels so adding muscle mass means better glucose absorption.

Other Diabetes Medications

There’s medications for people with type 2 diabetes that not only help with blood glucose control but also with weigh management. These include Semaglutides like Ozempic and the newer drug Tirzepatide.


Gaining weight is a common side effect experienced by people taking insulin. Because the insulin helps absorb glucose from the blood, any excess glucose stored in the muscles can become fat and lead to weight gain.

But the many benefits of insulin definitely outweigh the drawbacks of gaining weight. Insulin has a proven record of safety and effectiveness, is a more natural treatment option than medications, and dosage can be easily adjusted to meet your needs.

And best of all, there are simple ways to lessen the chances of gaining weight. Adjusting insulin dose, watching carb intake and regular exercise can help you maintain a healthy weight and are important for diabetes self care.

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