A banana can raise your blood sugar, but how quickly that happens depends on how ripe the banana is.
The ripeness of a banana can determine how quickly it raises blood sugar.
A Slower Increase: A Just-Ripe Banana
A just-ripe banana that’s yellow with maybe a green tip generally has a low glycemic index of 51. The glycemic index is a scale from 0-100 that measures the impact of foods on blood sugar, with lower numbers meaning a slower rise in blood sugar.
A Faster Increase: A Ripe Banana
As the banana softens and develops brown spots, its glycemic index increases to around 58, which bumps it into the medium-glycemic index range. Ripening turns the banana’s starch into simple sugars, and those sugars enter your bloodstream more quickly than the starch in a less-ripe banana.
The fiber content of bananas also decreases as they ripen. Fiber slows digestion and helps keep blood sugar from rising too quickly. So an overripe banana with less fiber and more sugar can raise your blood glucose faster than one that’s less ripe.
A banana can increase blood sugar because the fruit is rich in carbohydrates. When bananas are green, those carbs are mostly in the form of starch. Your body breaks down that starch into glucose (sugar), so any banana will raise your blood sugar to some degree.
A few adjustments can help you enjoy bananas without causing blood sugar spikes:
- Choose just-ripe bananas: Yellow bananas with green tips have less sugar and more fiber than overripe ones.
- Stick to smaller portions: A small banana has fewer carbs than a large one, which means less impact on your blood sugar.
- Add protein or healthy fats: Eating a banana with peanut butter, nuts, or Greek yogurt can slow down digestion and help prevent blood sugar from rising too quickly.
- Spread out your fruit: Instead of eating a whole banana at once, have half now and save the rest for later in the day.
If You Have Diabetes
If you have diabetes, the number of bananas you can have a day depends mostly on the size of the banana and the daily carb goal your healthcare provider recommends. One medium banana (about 7-8 inches long) has around 26 grams of carbs. For many people with diabetes, that’s close to an entire snack’s worth of carbohydrates.
To help with portion control, the American Diabetes Association recommends keeping fruit servings to about half a cup or one small piece per meal or snack. That means a small banana—or half of a medium or large one—is usually a more manageable choice for steady blood sugar. Eating a large banana or two small bananas at once adds more carbs at a time, which can lead to a faster rise in blood sugar.
