When you have diabetes, it’s important to keep your blood sugar levels as stable as possible.

Good blood sugar management can help prevent or slow the progression of some of the main medical complications of diabetes (1, 2).

For this reason, avoiding or minimizing foods that cause blood sugar spikes is essential.

Despite being a healthy fruit, bananas are pretty high in both carbs and sugar, which are the main nutrients that raise blood sugar levels.

This article investigates whether you can eat bananas if you have diabetes, as well as if they affect your blood sugar.

If you have diabetes, being aware of the amount and type of carbs in your diet is important.

This is because carbs raise your blood sugar level more than other nutrients, which means they can greatly affect your blood sugar management.

When blood sugar levels rise in people without diabetes, the body produces insulin. It helps move sugar out of the blood and into cells, where it’s used or stored.

However, this process doesn’t work as it should in people with diabetes. Instead, either the body doesn’t produce enough insulin, or the cells are resistant to the insulin that’s made.

If not managed properly, this can result in high carb foods causing blood sugar spikes or constantly high blood sugar levels, both of which are unhealthy.

How much sugar is in a banana?

One medium-sized banana (about 126 grams) contains 29 grams of carbs and 112 calories. The carbs are in the form of sugar, starch, and fiber (3).

A single medium-sized banana contains about 15 grams of sugar (3).

Summary

Bananas do contain simple carbs, which can cause blood sugar levels to rise more than other nutrients.

In addition to starch and sugar, a medium-sized banana contains 3 grams of fiber (3).

Everyone, including people with diabetes, should eat adequate amounts of dietary fiber due to its potential health benefits.

However, fiber is especially important for people with diabetes, as it can help slow the digestion and absorption of carbs (4).

This can reduce blood sugar spikes and improve overall blood sugar management (5).

One way of determining how a carb-containing food will affect blood sugars is by looking at its glycemic index (GI).

The glycemic index ranks foods based on how much and how quickly they raise blood sugar levels.

The scores run from 0 to 100 with the following classifications:

  • Low GI: 55 or less
  • Medium GI: 56 to 69
  • High GI: 70 to 100

Diets based on low GI foods are thought to be particularly good for people with type 2 diabetes (6, 7, 8, 9).

This is because low GI foods are absorbed more slowly and cause a more gradual rise in blood sugar levels, rather than large spikes.

Overall, bananas score between low and medium on the GI scale (between 42 to 62, depending on the ripeness) (10).

Summary

In addition to sugar and starch, bananas contain some fiber. This means that the sugars in bananas are more slowly digested and absorbed, which could prevent blood sugar spikes.

The type of carbs in your banana depends on the ripeness.

Green or unripe bananas contain less sugar and more resistant starch (11, 12).

Resistant starches are long chains of glucose (starch) that are “resistant” to digestion in the upper part of your digestive system (13).

This means that they function similarly to fiber and won’t cause a rise in blood sugar levels.

They also may help feed the friendly bacteria in your gut, which has been linked to improved metabolic health and better blood sugar management (14, 15, 16, 17).

In fact, a 2015 study on blood sugar management in women with type 2 diabetes found some interesting results. Those supplementing with resistant starch had better blood sugar management than those who didn’t over an 8-week period (18).

Other studies have indicated that resistant starch may have beneficial effects in people with type 2 diabetes. These include improving insulin sensitivity and reducing inflammation (19, 20, 21, 22).

The role of resistant starch in type 1 diabetes is less clear.

A banana’s effect on blood sugar depends on its ripeness

Yellow or ripe bananas contain less resistant starch than green bananas, as well as more sugar, which is more quickly absorbed than starch.

This means that fully ripe bananas have a higher GI and will cause your blood sugar to rise faster than green or unripe bananas (12).

Summary

Green (unripe) bananas contain resistant starch, which doesn’t raise blood sugar levels and may improve long-term blood sugar management. Yellow, ripe bananas contain more sugar than green ones, so they may cause a bigger rise in your blood sugar level.

Ripeness isn’t the only factor when it comes to the amount of sugar in your banana — size also matters. The bigger the banana, the more carbs you will be getting.

This means that a larger banana will have a greater effect on your blood sugar level. This portion-size effect is called the glycemic load.

Glycemic load is calculated by multiplying the glycemic index of a food by the number of carbs in a serving, then dividing that number by 100.

A score of less than 10 is considered low, 11 to 19 is medium, and more than 20 is high.

Bananas vary in size, from about 18.5 to 35 grams.

If a banana was fully ripe (GI of 62), then its glycemic load would range from 11 for a very small banana to 22 for a very large banana.

To ensure you don’t cause your blood sugar to rise too much, it’s important to be aware of the size of the banana you’re eating.

Summary

The size of the banana you eat determines its effect on your blood sugar level. The larger the banana, the more carbs you’ll consume and the greater the rise in your blood sugar.

Most general dietary guidelines for diabetes recommend following a healthy, balanced diet that includes fruit (23, 24, 25).

This is because eating fruits and vegetables has been linked to better health and a lower risk of disease, such as heart disease and some cancers (26, 27, 28, 29).

People living with diabetes are at an even greater risk of these diseases, so eating enough fruits and vegetables is important (30, 31, 32, 33).

Unlike refined sugar products like candy and cake, the carbs in fruits such as bananas come with fiber, antioxidants, vitamins, and minerals.

More specifically, bananas provide fiber, potassium, vitamin B6, and vitamin C. They also contain some antioxidants and beneficial plant compounds (34).

For most people with diabetes, fruits (including bananas) are a healthy choice.

Although, if you’re following a low carb diet to manage your diabetes, even a small banana contains around 22 grams of carbs, which may be too much for your eating plan.

If your healthcare provider thinks you’re able to eat bananas, it’s important to be mindful of the ripeness and size of the banana to reduce its effect on your blood sugar level.

Summary

Fruits like bananas are a healthy food that contains fiber, vitamins, and minerals. You can include bananas in your diet, even if you have diabetes. Always confirm your eating plan with your healthcare provider first.

If you have diabetes, it’s possible to enjoy fruit such as bananas as part of a healthy eating plan.

If you enjoy bananas, the following tips could help minimize their effects on your blood sugar levels:

  • Watch your portion size. Eat a smaller banana to reduce the amount of sugar you eat in one sitting.
  • Choose a firm, nearly ripe banana. Pick a banana that’s not overly ripe so that the sugar content is slightly lower.
  • Spread your fruit intake throughout the day. Spread out your fruit intake to help reduce the glycemic load and keep your blood sugar levels stable.
  • Eat them with other foods. Enjoy your bananas with other foods, such as nuts or full fat yogurt, to help slow the digestion and absorption of the sugar.

If you have diabetes, remember that carb-containing foods can affect people’s blood sugars differently.

Therefore, you might want to monitor how eating bananas affects your blood sugar and adjust your eating habits accordingly.