How Many Carbs in a Banana? By Size, Ripeness & Net Carbs

A banana changes its own nutrition while it sits on your counter. Bought green, it holds most of its carbohydrate as starch, much of it a kind your body doesn't digest; a few days later, that starch has become the sugar that makes a speckled banana taste so sweet.23

USDA's nutrition record for bananas doesn't separate one stage from another,3 so the familiar carb count describes an average banana, and size is what moves that count. An extra-small banana carries 18.5 grams of carbohydrate and an extra-large one 34.7 grams.1 Ripeness changes the kind of carbohydrate inside, and that's what your blood sugar responds to.2

Bananas made the fruit list in The Biblio Diet, my book with Jordan Rubin, which names organic fresh or frozen fruit as the best choice.5 When I talked on my show about satisfying a sweet tooth, bananas came up by name:6

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How many carbs are in a banana?

These counts come from USDA FoodData Central's record for raw bananas, worked out at USDA's own weight for each size.1

Carbs in one banana by size, from USDA FoodData Central (Bananas, raw, FDC 173944) at USDA's portion weights. Net carbs are worked out before rounding, so a row can differ by 0.1 gram from subtracting the rounded columns.1

A medium banana's 27.0 grams is about 10% of the 275-gram daily value for carbohydrate.17 If you weigh your fruit, USDA's record works out to 22.84 grams of carbohydrate and 2.6 grams of fiber per 100 grams, or about 20.2 grams of net carbs.1 Bananas are about three-quarters water by weight, 74.9 grams in every 100, so their carbohydrate comes packed with water and fiber.1

How many net carbs are in a banana?

Net carbs are the number to watch on keto and other low-carb plans, which hold them to about 20 to 50 grams a day.8 The keto section below shows where a banana fits.

Green bananas change the math in your favor. USDA's banana record makes no distinction by ripeness, and its fiber figure comes from an older lab method that doesn't capture the resistant starch in green fruit.3 When researchers at Virginia Tech and the USDA tested one shipment of bananas both ways at four stages of ripeness, unripe fruit measured 17.9 grams of fiber per 100 grams with the newer method, which counts resistant starch as fiber, against 1.4 grams with the older one. By the overripe stage, the two methods were close, at 1.6 and 1.1 grams.3 So a greener banana gives you fewer digestible carbs than the standard count suggests.

How much sugar is in a banana?

USDA works out total carbohydrate as what's left after water, protein, fat and minerals are measured, so the sugar, starch and fiber figures don't add up to the total exactly.1 The split between sugar and starch also depends on ripeness, as the next section shows.

The sugar in a banana is a different thing from the sugar in a soda. I've made this point on my show before: sugar itself isn't the culprit; the trouble is sugar that comes without the fiber and nutrients of a whole food.6 A banana delivers its sugar with fiber, water, potassium and vitamin B6, while a soda or a candy bar brings sugar with little else. For the limits that apply to added sugar, see how much sugar per day and the hidden sugar foods that add it without your noticing.

How does ripeness change a banana's carbs?

For that analysis, researchers at Virginia Tech and the USDA took one shipment of Cavendish bananas, the everyday grocery variety, and tested medium-size fruit at four stages, from green to speckled, averaging 3 samples of 3 to 5 bananas at each stage.3

What ripening does to a banana's carbs, in grams per 100 grams of banana. Averages of the 3 samples at each stage, from the study's supplementary data. The starch test and the newer fiber test both pick up resistant starch, so these columns aren't meant to be added together.3

Bananas bought from stores told the same story. In the same study's samples from several suppliers, starch averaged 4.50 grams per 100 grams in slightly ripe fruit, 2.52 grams in ripe fruit and 0.48 grams in overripe fruit, while total sugars ran from 15.0 to 17.1 grams across the three stages, with no statistically significant difference between them.3 Once a banana is yellow, its sugar stays in about the same range while the last of its starch keeps shrinking.

Here's what that starch does once you eat a green banana:

Each of a banana's stages has its use. Reach for a greener banana when you want a gentler rise in blood sugar and more resistant starch for your gut, and a ripe one when you want quick fuel before exercise or natural sweetness in a recipe. If you'd like that starch without eating firm green fruit, green banana flour is made from unripe bananas.

What is the glycemic index of a banana?

That 51 comes from the 2008 international glycemic index tables, which average the results of testing from multiple labs, and it puts bananas among the low-glycemic foods.4 Glycemic load multiplies a food's glycemic index by the digestible carbohydrate in a serving and divides by 100. For a medium banana, 51 × 23.9 ÷ 100 comes to about 12.41

Ripeness moves the number. In a Danish study, 10 adults with type 2 diabetes each ate three test meals on separate days: 120 grams of under-ripe banana (about one medium banana), 120 grams of over-ripe banana and 40 grams of white bread. Over the next 4 hours, the under-ripe banana produced the smallest blood-sugar response, 62, against 106 for the over-ripe banana and 181 for the bread, and both bananas raised blood sugar significantly less than the bread did.2 Insulin responses were similar after all three meals.2

Banana benefits, ranked by evidence

Human research on bananas, and on the starch in green bananas, supports five benefits, ranked here by the strength of that evidence: steady fuel for exercise, potassium for healthy blood pressure, a gentler blood-sugar rise from greener fruit, food for your gut bacteria, and a lower type 2 diabetes risk when bananas replace fruit juice.

Do bananas spike blood sugar?

A whole-food carbohydrate like a banana gives a moderate rise, and you can soften it. On my show, I've put the fix in three steps:24

The research backs both the food order and the walk. In a small pilot study, 11 adults with type 2 diabetes who took metformin ate the same meal of bread, orange juice, chicken and vegetables on two days a week apart, carbohydrates first on one day and last on the other. With the carbohydrates last, their blood sugar ran 28.6% lower at 30 minutes, 36.7% lower at 60 minutes and 16.8% lower at 2 hours.25 And in a randomized trial in which 41 adults with type 2 diabetes each tried both plans for 2 weeks, the rise in blood sugar over the 3 hours after meals was 12% smaller with a 10-minute walk after each main meal than with one 30-minute walk a day, and 22% smaller after the evening meal.26

My protocols put the rule simply: never eat carbs naked; always pair them with protein or fat.27 My Insulin Resistance & Prediabetes protocol builds the day around it, with vegetables and protein first, carbohydrates last and a 10- to 15-minute walk after your two biggest meals.28 Timing helps, too. In the same episode, I described a breakfast built on one serving of fruit with plenty of protein and some extra fiber, and I said the ideal is very low carb at night, with protein, fat and fiber at dinner.24 That makes breakfast, lunch or the hour around a workout the natural place for a banana. For more ways to keep the curve flat, see normal blood sugar and the insulin resistance diet.

If you'd like to see your own response, my Type 2 Diabetes Protocol suggests wearing a continuous glucose monitor for two weeks to expose the spikes.29

Can you eat bananas if you have diabetes?

If you've been diagnosed with diabetes, weight gain, cardiovascular issues, metabolic syndrome, PCOS, inflammatory conditions or Candida overgrowth, my guideline is two servings of fruit a day from a low-sugar list that leaves bananas out: avocado, lemons, limes, strawberries, blueberries, apples (especially green apples with the skin), blackberries, olives and grapefruit.5 If you're healthy and active, it's three to four servings of fruit a day, and I hold that some fruit is always better than none.5

One small study has tested daily bananas in diabetes. In a study with no comparison group, 15 adults with type 2 diabetes ate 250 grams of banana, about two medium bananas, at breakfast every day for 4 weeks. Adiponectin, a hormone that helps insulin do its job, rose from 37.5 to 48.8 ng/mL, while their blood sugar and blood fats didn't change significantly. In 30 adults with high cholesterol in the same study, who ate 250 or 500 grams a day for 12 weeks, fasting blood sugar fell within 4 weeks, from 99 to 92 mg/dL and from 102 to 92 mg/dL, and stayed lower through week 12, and their ratio of LDL to HDL cholesterol improved, from 2.7 to 2.1 and from 2.8 to 2.5.30 For a full plan, see the diabetic diet plan.

If you take medication to lower your blood sugar, read the safety section below before you change how you eat.

Are bananas keto?

Keto plans hold net carbs to about 20 to 50 grams a day, and staying near 20 grams is what moves most people into ketosis within a few days.8 One banana would use up a strict day on its own, which is why the keto diet food list sets bananas aside with other healthy carbs, such as sweet potatoes and beans. The fruit that fits keto is berries in small amounts, plus lemon and lime;8 see keto fruit for the amounts.

Setting bananas aside on keto is temporary. In one episode, I said I really like a ketogenic diet for certain conditions, but I don't typically like it long term, for more than about three months at a time; after that, you add some carbs back in.31 That's when bananas come back to the table.

You don't have to go keto to eat well for blood sugar, either. My Type 2 Diabetes Protocol says you need not be strictly keto: cut refined carbs and sugar, lead with protein and fiber, and choose a carb level you can sustain.29 To find your own range, see how many grams of carbs per day.

What else is in a banana?

Beyond its carbs, a medium banana gives you about a quarter of a day's vitamin B6, plus useful amounts of manganese, vitamin C, fiber and potassium, for 105 calories and almost no fat.17

Calculated from USDA FoodData Central record 173944 (Bananas, raw) at USDA's 118-gram medium banana. % Daily Value uses FDA reference values.17

For a fruit, that's a strong share of vitamin B6. For what a banana's potassium does for blood pressure, see the benefits section above.

How should you eat a banana for steady blood sugar?

These habits give you a banana's fuel and nutrients with a gentler rise in blood sugar:

• Pair it with protein or fat. Slice it over plain A2 or goat-milk Greek yogurt or kefir, or eat it with a handful of almonds or walnuts or a couple of eggs.27

• Eat it earlier in the day. Breakfast, lunch or the hour around a workout suits a banana better than dinner, since the ideal dinner is very low carb.24

• Choose a greener banana for a gentler rise. Yellow with green tips still carries more starch than a speckled one.32

• Walk for 10 minutes after the meal. A short walk after each main meal lowered after-meal blood sugar in adults with type 2 diabetes.26

• Keep smoothies to one banana, with protein. Blend it with a scoop of protein powder,14 a handful of greens and unsweetened almond milk; see these healthy smoothie recipes for more.

• Sweeten with it, in small amounts. When a recipe needs sweetness, a little raw honey or mashed ripe banana can stand in for refined sugar.6

• Freeze ripe bananas. Peel and slice them before they go too soft, then freeze them for smoothies or blend them on their own into a soft-serve dessert.

Banana side effects and who should be careful

If you take medication for blood sugar

Never stop or change a diabetes medication on your own. As your numbers improve with the habits on this page, bring your labs and home readings to your prescriber and let them adjust your doses, as the Type 2 Diabetes Protocol explains.29

Potassium, kidney disease and blood pressure medicines

A medium banana carries 422 milligrams of potassium.1 In people with chronic kidney disease, or who take medicines such as ACE inhibitors or potassium-sparing diuretics, even dietary potassium below the usual recommended intake can cause hyperkalemia, too much potassium in the blood, and NIH's Office of Dietary Supplements also lists angiotensin receptor blockers (ARBs) among the blood pressure medicines that can raise potassium.15 If one of these applies to you, ask your doctor how much potassium is right for you before adding high-potassium foods.

Banana and latex allergy

Banana is among the fruits most often linked to latex allergy, along with avocado, kiwi and papaya, because their proteins can cross-react.32 If bananas make your mouth itch or your lips swell, stop eating them and see an allergist; throat swelling or trouble breathing is an emergency, so call 911. See food allergy symptoms for the signs.

The bottom line

How many carbs in a banana: frequently asked questions

References

1. U.S. Department of Agriculture, Agricultural Research Service. Bananas, raw. FoodData Central, SR Legacy, FDC ID 173944 (NDB 9040). Published April 1, 2019. Per-portion values computed from the record's per-100-gram values (carbohydrate by difference 22.84 g, fiber 2.6 g) at USDA's portion weights: extra small 81 g, small 101 g, medium 118 g, large 136 g, extra large 152 g, 1 cup sliced 150 g, 1 cup mashed 225 g. Accessed October 8, 2026.
2. Hermansen K, Rasmussen O, Gregersen S, Larsen S. Influence of ripeness of banana on the blood glucose and insulin response in type 2 diabetic subjects. Diabet Med. 1992;9(8):739-43. doi:10.1111/j.1464-5491.1992.tb01883.x. PMID:1395467
3. Phillips KM, McGinty RC, Couture G, Pehrsson PR, McKillop K, Fukagawa NK. Dietary fiber, starch, and sugars in bananas at different stages of ripeness in the retail market. PLoS One. 2021;16(7):e0253366. doi:10.1371/journal.pone.0253366. PMID:34237070. Ripening-study values: S1 Table (medium fruit, mean of 3 composites per stage); retail values: Table 2.
4. Atkinson FS, Foster-Powell K, Brand-Miller JC. International tables of glycemic index and glycemic load values: 2008. Diabetes Care. 2008;31(12):2281-3. doi:10.2337/dc08-1239. PMID:18835944
5. Axe J, Rubin J. The Biblio Diet. Hachette Book Group; 2025. ISBN 9781546008439. Food lists ("Fruits"); fruit chapter (fruit servings guidance and the low-sugar fruit list).
6. Axe J. 11 Foods with SHOCKINGLY High Amounts of Sugar (Best Sugar Substitutes). The Dr. Josh Axe Show (episode). 2024. Lines cited at 22:15, 22:43 and 22:54 (pull quote). YouTube: https://www.youtube.com/watch?v=KG7_2ZYmHLU&t=1335s
7. U.S. Food and Drug Administration. Daily Value on the Nutrition and Supplement Facts Labels.
8. DrAxe.com. Keto Diet: Benefits, Food List, 7-Day Meal Plan & How to Start (A Doctor's Guide). 2026. Section "Keto macros & net carbs."
9. Pugh JE, Cai M, Altieri N, Frost G. A comparison of the effects of resistant starch types on glycemic response in individuals with type 2 diabetes or prediabetes: A systematic review and meta-analysis. Front Nutr. 2023;10:1118229. doi:10.3389/fnut.2023.1118229. PMID:37051127
10. Englyst HN, Cummings JH. Digestion of the carbohydrates of banana (Musa paradisiaca sapientum) in the human small intestine. Am J Clin Nutr. 1986;44(1):42-50. doi:10.1093/ajcn/44.1.42. PMID:3014853
11. Koh A, De Vadder F, Kovatcheva-Datchary P, Bäckhed F. From Dietary Fiber to Host Physiology: Short-Chain Fatty Acids as Key Bacterial Metabolites. Cell. 2016;165(6):1332-1345. doi:10.1016/j.cell.2016.05.041. PMID:27259147
12. Nieman DC, Gillitt ND, Henson DA, Sha W, Shanely RA, Knab AM, et al. Bananas as an energy source during exercise: a metabolomics approach. PLoS One. 2012;7(5):e37479. doi:10.1371/journal.pone.0037479. PMID:22616015
13. Nieman DC, Gillitt ND, Sha W, Esposito D, Ramamoorthy S. Metabolic recovery from heavy exertion following banana compared to sugar beverage or water only ingestion: A randomized, crossover trial. PLoS One. 2018;13(3):e0194843. doi:10.1371/journal.pone.0194843. PMID:29566095
14. Axe J. Creatine Isn't Just for Muscle: What It Does for Your Brain, Energy and Healthy Aging. The Dr. Josh Axe Show (episode). 2026. Line cited at 20:55. YouTube: https://www.youtube.com/watch?v=bqe0ZGM4U1g&t=1255s
15. National Institutes of Health, Office of Dietary Supplements. Potassium: Fact Sheet for Health Professionals. Updated June 2, 2022. Read October 8, 2026.
16. Aburto NJ, Hanson S, Gutierrez H, Hooper L, Elliott P, Cappuccio FP. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. 2013;346:f1378. doi:10.1136/bmj.f1378. PMID:23558164
17. Axe J. The High Blood Pressure Protocol. DrAxe.com; 2026. The Pressure Reset, Remineralize phase (eat-freely foods; potassium target from food).
18. Axe J. How to Hydrate Your Brain, Boost Energy & End Brain Fog. The Dr. Josh Axe Show (episode). 2025. Lines cited at 22:48 to 23:51. YouTube: https://www.youtube.com/watch?v=8nmGynV_jjQ&t=1368s
19. Costa ES, França CN, Fonseca FAH, Kato JT, Bianco HT, Freitas TT, et al. Beneficial effects of green banana biomass consumption in patients with pre-diabetes and type 2 diabetes: a randomised controlled trial. Br J Nutr. 2019;121(12):1365-1375. doi:10.1017/S0007114519000576. PMID:30887937
20. Falcomer AL, Riquette RFR, de Lima BR, Ginani VC, Zandonadi RP. Health Benefits of Green Banana Consumption: A Systematic Review. Nutrients. 2019;11(6):1222. doi:10.3390/nu11061222. PMID:31146437
21. Axe J. The Shocking Reason Your Anxiety, Brain Fog & Bloating May Start in Your Gut. The Dr. Josh Axe Show (episode). 2026. Lines cited at 38:58 to 39:18. YouTube: https://www.youtube.com/watch?v=yumJczZ1_JM&t=2338s
22. Muraki I, Imamura F, Manson JE, Hu FB, Willett WC, van Dam RM, et al. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ. 2013;347:f5001. doi:10.1136/bmj.f5001. PMID:23990623
23. Alperet DJ, Butler LM, Koh WP, Yuan JM, van Dam RM. Influence of temperate, subtropical, and tropical fruit consumption on risk of type 2 diabetes in an Asian population. Am J Clin Nutr. 2017;105(3):736-745. doi:10.3945/ajcn.116.147090. PMID:28179225
24. Axe J. The Real Reason You Wake Up Tired Every Morning. The Dr. Josh Axe Show (episode). 2026. Lines cited at 5:59 (pull quote), 6:13 and 6:36. YouTube: https://www.youtube.com/watch?v=UYvHrFB_g50&t=359s
25. Shukla AP, Iliescu RG, Thomas CE, Aronne LJ. Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels. Diabetes Care. 2015;38(7):e98-9. doi:10.2337/dc15-0429. PMID:26106234
26. Reynolds AN, Mann JI, Williams S, Venn BJ. Advice to walk after meals is more effective for lowering postprandial glycaemia in type 2 diabetes mellitus than advice that does not specify timing: a randomised crossover study. Diabetologia. 2016;59(12):2572-2578. doi:10.1007/s00125-016-4085-2. PMID:27747394
27. Axe J. The PCOS Protocol. DrAxe.com; 2026. "What to do" panel (never eat carbs naked; always pair them with protein or fat).
28. Axe J. Insulin Resistance & Prediabetes: The 90-Day Healing Protocol. DrAxe.com; 2026. Phase 1, "Stabilize" (eat in order; walk after your two biggest meals).
29. Axe J. The Type 2 Diabetes Protocol. DrAxe.com; 2026. Troubleshooting & FAQ, p. 22 (wearing a CGM for two weeks; medication changes only with your prescriber; "Do I have to go keto?").
30. Cressey R, Kumsaiyai W, Mangklabruks A. Daily consumption of banana marginally improves blood glucose and lipid profile in hypercholesterolemic subjects and increases serum adiponectin in type 2 diabetic patients. Indian J Exp Biol. 2014;52(12):1173-81. PMID:25651610. Full text: Tables 5-7.
31. Axe J. Top 12 Foods & Herbs for Weight Loss (BETTER THAN OZEMPIC). The Dr. Josh Axe Show (episode). 2025. Lines cited at 26:17 to 26:47. YouTube: https://www.youtube.com/watch?v=-Uq92QA3MKw&t=1577s
32. Gromek W, Kołdej N, Świtała S, Majsiak E, Kurowski M. Revisiting Latex-Fruit Syndrome after 30 Years of Research: A Comprehensive Literature Review and Description of Two Cases. J Clin Med. 2024;13(14):4222. doi:10.3390/jcm13144222. PMID:39064262

Dr. Josh Axe, DC, DNM, CNS

Doctor of Natural Medicine · Founder, DrAxe.com

Dr. Axe is a certified doctor of natural medicine, clinical nutritionist, and multiple New York Times bestselling author. He has spent 20+ years in clinical practice helping people heal at the root cause and founded one of the most-visited natural-health platforms in the world.

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