Portobello Mushroom Glycemic Index
Low GI · The honest verdict
Gentle on blood sugar
Glycemic index
15
per source
Glycemic load
1
Low GL
This food's glycemic index is 15, which is Low GI.
Portobello mushrooms are an ideal food for blood sugar management. With only about 2 g of net carbs per 100 g serving and a glycemic load of 1, they have virtually no effect on blood glucose. They are rich in B vitamins, selenium, and potassium while being low in calories. This is general nutrition information, not medical advice — people with diabetes should confirm dietary choices with their care team.
GI numbers vary by source, ripeness, and how a food is prepared. This is general nutrition information — not medical advice. If you manage diabetes, confirm specifics with your care team.
Key facts
Portobello mushrooms have an estimated GI of around 15 — among the lowest of any food.
One 100 g serving of grilled portobello mushrooms contains only 2.1 g of net carbs.
Portobellos are one of the few natural food sources of vitamin D when exposed to UV light during growth.
What's actually inside
Per 100 g, with your typical serving noted as 100 g (about 1 medium cap), grilled. The carb family is what moves blood sugar — fiber is the number that softens the spike.
Total carbs
3.3g
Net carbs
2.1g
total carbs minus fiber
Fiber
1.2g
slows the glucose rise
- Sugars
- 1.7g
- Protein
- 3.1g
- Calories
- 29kcal
Notable nutrients
- Niacin (Vitamin B3)4.5 mg
- Pantothenic Acid (B5)1.5 mg
- Selenium18.6 mcg
- Potassium364 mg
- Copper0.3 mg
Is it a smart choice for blood sugar?
GI is only half the story — portion (glycemic load) and what you eat it with decide the real-world effect. Here's the honest read.
The verdict
Excellent — very low carb, negligible blood sugar impact
Portobello mushrooms are an ideal food for blood sugar management. With only about 2 g of net carbs per 100 g serving and a glycemic load of 1, they have virtually no effect on blood glucose. They are rich in B vitamins, selenium, and potassium while being low in calories. This is general nutrition information, not medical advice — people with diabetes should confirm dietary choices with their care team.
Portion guidance
Portion size is not a meaningful concern with portobello mushrooms due to their very low carb content. A typical serving of one large grilled cap (about 100 g) contains roughly 2 g of net carbs. Even a generous serving of 200–300 g would still have a very low glycemic load. They can be used freely as a vegetable side, burger substitute, or salad topping without significantly affecting blood sugar.
This is general nutrition information, not personal medical advice. Blood sugar responses are individual — if you have diabetes or prediabetes, your care team can tell you how this fits your plan.
How to keep the spike small
The same food can land differently depending on how it's cooked and what it's eaten with. Use these levers to your advantage.
Grilling or roasting
Little effectGrilling or roasting portobellos reduces moisture content, concentrating nutrients slightly but not meaningfully changing the glycemic response since the carbohydrate content is already very low.
Marinating in oil and vinegar
Lowers the spikeAdding a vinegar-based marinade introduces acetic acid, which can modestly slow gastric emptying and further blunt any blood sugar response from the small amount of carbs present.
Stuffing with breadcrumbs or grains
Raises GIStuffed portobello recipes that add breadcrumbs, rice, or other high-carb fillings will raise the overall glycemic impact of the dish, but the mushroom itself remains low-GI.
Pairing tip
Portobello mushrooms pair well with any protein or non-starchy vegetable without concern for blood sugar. Use them as a burger bun replacement to reduce the carb load of a meal. For a balanced plate, serve grilled portobellos alongside lean protein and leafy greens. They also work well in stir-fries with other low-GI vegetables.
Why GI numbers vary
GI data for mushrooms is limited because they contain so few carbohydrates that glycemic testing is rarely performed. The value of around 15 is estimated based on the very low carb content and high fiber-to-carb ratio. Mushrooms are generally considered negligible-GI foods. Different mushroom varieties (white button, cremini, portobello) have nearly identical nutritional profiles, so the GI is consistent across types.
Not medical advice. This page is general nutrition information about Portobello Mushroom. It isn't a diagnosis or a treatment plan. If you have diabetes, prediabetes, or another condition affecting blood sugar, confirm any dietary decisions with your doctor or care team.
❓Frequently Asked Questions
Portobello mushrooms have a very low glycemic index, estimated around 15. Because they contain only about 3 g of total carbs per 100 g — most of which is fiber — they have a minimal effect on blood sugar. The GI is so low that mushrooms are often classified as a negligible-GI food. This makes them one of the safest vegetable choices for blood sugar management.
Yes, portobello mushrooms are excellent for people with diabetes. With roughly 2 g of net carbs per 100 g serving and a glycemic load of 1, they will not cause meaningful blood sugar elevation. They also provide important nutrients like B vitamins, selenium, and potassium. As with all dietary choices, individual responses vary — this is general nutrition information, not medical advice.
Portobello mushrooms contain about 3.3 g of total carbohydrates per 100 g, of which 1.2 g is fiber. This leaves roughly 2.1 g of net carbs — an extremely low amount. They are considered a low-carb food and fit easily into keto, low-carb, and diabetes-friendly diets without concern.
Absolutely. With only about 2 g of net carbs per 100 g serving, portobello mushrooms are a staple on keto and other very low-carb diets. They are versatile as a burger substitute, grilled side dish, or addition to salads and omelets. Even large portions remain well within daily carb limits.
Cooking portobellos reduces their water content, which concentrates nutrients slightly by weight. Grilling or roasting brings out a meaty, umami flavor without adding carbs. The glycemic impact remains negligible regardless of cooking method, as long as no high-carb ingredients like breadcrumbs or sugary marinades are added.
Related Articles
Oyster Mushroom Glycemic Index, Load & Nutrition
Oyster mushrooms have a very low glycemic index (about 15) and negligible glycemic load — excellent for blood sugar. Full nutrition facts and diabetes-friendly tips inside.
Read moreEnoki Mushroom Glycemic Index, Load & Nutrition
Enoki mushrooms have a low glycemic index around 30 and negligible glycemic load. Full nutrition facts, diabetes-friendly verdict, and prep tips inside.
Read moreShiitake Mushroom Glycemic Index, Load & Nutrition
Shiitake mushrooms have a negligible glycemic index — very low carb content makes them excellent for blood sugar. Honest GI info, glycemic load, nutrition facts, and diabetes tips inside.
Read moreEating well is easier when allergies aren't in the way
Curex helps people find and treat the allergies behind everyday symptoms with at-home testing and immunotherapy. If food or seasonal allergies make eating well harder than it should be, that's where we can help — no pressure, just here if you need it.
Curex focuses on allergies — not diabetes or blood-sugar care. For blood sugar, your primary care team is the right place to start.
Reviewed by
Curex Editorial TeamReviewed for accuracy
Last reviewed July 2026