A banana is one of the easiest foods there is. It needs no knife, no plate and no cooking. So it can be a shock when someone says, soon after a diabetes diagnosis, that bananas are "too sweet" for you now.

Bananas do carry carbohydrate, and that carbohydrate raises blood glucose. But the useful questions are how big the banana is, how ripe it is, and how it fits into the rest of your day. This article goes through what is known, and what is not.

What one banana holds

Here is a raw banana at one medium fruit, as USDA FoodData Central measures it:

Open the food page to see fiber and total sugars under the carbohydrate. A banana is not one carb choice in a neat package. Depending on its size, it can be close to one choice or nearer two. If "carb choice" is a new term, our article What is a carb choice? explains it.

Size matters more than many people expect. USDA measures bananas from "extra small" to "extra large", and the food page lets you pick each one. The difference between a small banana and a very large one is real. Comparing the banana in your fruit bowl with those sizes once is a simple way to know what you are counting.

Dried banana is a different amount

Drying takes the water out of fruit and leaves the carbohydrate behind. So a cup of dried banana is a very different food from a cup of fresh banana:

Compare that card with the fresh banana above. A cup of the dried fruit holds several times the carbohydrate of one medium banana. Dried fruit is easy to eat by the handful, so the amount is the part to watch. On the food page you can set a smaller amount, such as a tablespoon.

Green or yellow: does ripeness matter?

As a banana ripens, its starch turns into sugar. In an under-ripe banana, starch makes up most of the carbohydrate. In a ripe one, much more of it is free sugar. This has led to the idea that a greener banana raises blood glucose less.

Two small studies tested this in people with type 2 diabetes, and they did not agree:

  • Hermansen and colleagues (1992) gave 10 people with type 2 diabetes under-ripe banana, over-ripe banana or white bread on separate days. In that study, the under-ripe banana produced a lower blood glucose response than the over-ripe one, and both were lower than white bread.
  • Ercan and colleagues (1993) gave 7 men with untreated type 2 diabetes bananas at four stages, from more yellow than green to yellow with brown flecks, each with the same amount of carbohydrate. They found the glucose and insulin responses "varied little with ripeness".

Both studies are small and more than thirty years old. One found a difference and one did not. So the honest answer is that the effect of ripeness is not settled. What both agree on is that a banana carries carbohydrate whatever its colour, and the amount still counts.

What large studies say about bananas and diabetes risk

A large study from the United States looked at whole fruit and the risk of developing type 2 diabetes. Muraki and colleagues (2013) followed about 187,000 nurses and other health professionals for many years. Eating more whole fruit overall was linked with a slightly lower risk of type 2 diabetes.

The study also looked at single fruits. For bananas, three more servings a week was linked with a small reduction in risk. Some fruits showed stronger links, and fruit juice was linked with a higher risk. (Juice has its own article: Fruit juice and diabetes.)

This was an observational study. It shows a link, not that bananas lower risk. People who eat more fruit may also differ in other ways. And it was about developing diabetes, not about managing diabetes you already have.

What guidelines say about fruit

The American Diabetes Association's Standards of Care include "whole fruits" among the foods an eating pattern for diabetes can emphasise. Its table of eating advice says fruits, "especially whole fruit", fresh, frozen, or canned in their own juice, "are all acceptable fruit options".

NIDDK, part of the US National Institutes of Health, lists fruit among the foods a healthy meal plan for diabetes may include. It also notes that some fruits have more carbs than others. In its plate method, fruit sits in the quarter of the plate for carbohydrate foods.

So a banana is not a "forbidden" food in these guidelines. It is a carbohydrate food, counted like any other.

If you take insulin or medicine that can cause lows

If you take mealtime insulin, a banana counts in the carbohydrate for that meal or snack. If you take fixed insulin doses, your care team may have asked you to keep your carbohydrate fairly steady from day to day. Adding or dropping fruit can change your glucose, in either direction. With insulin or another medicine that can cause low blood glucose, eating less carbohydrate than usual can raise the risk of a low. Talk to your diabetes team before making a big change, so your medicine can be adjusted if needed.

Also have kidney disease?

Bananas are known for potassium, which matters for many people with chronic kidney disease. That is a separate question from carbohydrate. Our sister site, KidneyFoods, covers potassium per serving. Your kidney team sets your potassium limits.

Seeing it in your day

Bananas can still have a place in your eating. What usually helps is knowing the size you eat and counting it with the rest of the meal. The Today page adds up what you log, so you can see where a banana fits in your day.

For other fruits, see mango and diabetes and durian and diabetes.

Your numbers are yours

How much carbohydrate fits in your meals depends on your medicines, your glucose goals and your body. Your doctor, diabetes educator or dietitian sets those numbers, and their advice comes before anything you read here. If fruit is an important part of how you eat, tell them, and ask how it can fit into your plan.

Sources

  • Hermansen K, Rasmussen O, Gregersen S, et al. Influence of ripeness of banana on the blood glucose and insulin response in type 2 diabetic subjects. Diabetic Medicine, 1992; 9(8): 739–743. pubmed.ncbi.nlm.nih.gov/1395467 (checked 8 October 2026)
  • Ercan N, Nuttall FQ, Gannon MC, et al. Plasma glucose and insulin responses to bananas of varying ripeness in persons with noninsulin-dependent diabetes mellitus. Journal of the American College of Nutrition, 1993; 12(6): 703–709. pubmed.ncbi.nlm.nih.gov/8294726 (checked 8 October 2026)
  • Muraki I, Imamura F, Manson JE, et al. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ, 2013; 347: f5001. pubmed.ncbi.nlm.nih.gov/23990623 (checked 8 October 2026)
  • American Diabetes Association Professional Practice Committee. 5. Facilitating Positive Health Behaviors and Well-being to Improve Health Outcomes: Standards of Care in Diabetes—2026. Diabetes Care, 2026; 49(Suppl 1): S89–S131 (recommendations 5.14 and 5.28, Table 5.2). pmc.ncbi.nlm.nih.gov/articles/PMC12690188 (checked 8 October 2026)
  • NIDDK. Healthy Living with Diabetes (last reviewed October 2023). niddk.nih.gov (checked 8 October 2026)
  • USDA FoodData Central: Bananas, raw (SR Legacy 173944); Bananas, dehydrated, or banana powder (SR Legacy 173945). fdc.nal.usda.gov (checked 8 October 2026)
  • Food figures on this page: USDA FoodData Central, via the DiabeticIndex food database.

This article is general information, not medical advice. Talk to your diabetes care team before changing how you eat or how you take your medicines.