Corn and Diabetes: Carbs, Glycemic Index and Portions

By the Diabetes Blogs editorial teamLast reviewed October 22, 2026

A medium ear of sweet corn has about 19 g of carbohydrate (17 g net). Glycemic index: low to medium (51 to 59). Yes, in measured portions. Corn is a starchy vegetable, so count it with the carbohydrates on your plate.

Sweet corn tastes like a vegetable and counts as a starch. A medium ear is a reasonable serving, and a cup of kernels is a bit more.

Corn does bring fiber, and cooked fresh corn sits in the lower-medium part of the glycemic index range. Creamed corn, corn chips and sweetened cornbread change the picture, because of added fat and sugar.

Carbs in corn by portion

Nutrients for Corn, sweet by portion
Portion	Grams	Carbs (g)	Fiber (g)	Net carbs (g)	Protein (g)
cup	145	27	2.9	24	4.8
ear, large	143	27	2.9	24	4.7
ear, medium	102	19	2	17	3.4
100 g (for comparing foods)	100	19	2	17	3.3

Source: USDA FoodData Central, FDC ID 169998 (Corn, sweet). Net carbs here means carbohydrate minus fiber. “Net carbs” is not an FDA-defined term, so total carbs are shown too. Values are estimates for a typical item; brands, ripeness and size vary.

Glycemic index and glycemic load

Glycemic index51 to 59Low to medium

Glycemic load, a medium ear of sweet corn9 to 10Low to medium GL

GI ranks how fast a food raises blood glucose compared with pure glucose (100). Low is 55 or less, medium 56 to 69, high 70 or more. Boiled, cooked and microwaved corn were all tested. Glycemic load multiplies the index by the available carbohydrate in a portion (carbs minus fiber), so it reflects how much you actually eat: low is 10 or less, medium 11 to 19, high 20 or more.

Which published values we used (3)

Entry	Food as listed	GI
Suppl. Table 1, #558	Sweet corn, cooked in microwave for 1.5 min	51
Suppl. Table 1, #559	Sweet corn, cooked	55
Suppl. Table 2, #2597	Sweet corn, boiled in water with 2 g salt	59

Atkinson FS et al. International tables of glycemic index and glycemic load values 2021. Am J Clin Nutr 2021;114(5):1625-1632. Glucose reference (glucose = 100); values from studies that used white bread were converted by the authors. Where studies differ we show the range, not an average.

Glycemic index is only one piece of the picture. The same food can give a different response depending on ripeness, cooking, what you eat it with and your own body, so your meter or CGM is the best guide.

How corn fit the plate method

Corn count toward the carbohydrate quarter of the plate in the plate method, along with grains, starchy vegetables, fruit and milk. The CDC describes the plate method as half non-starchy vegetables, a quarter protein and a quarter carbohydrate foods. See the diabetic meal plan guide for how it works, or drop corn onto a meal in the meal planner to watch the plate fill.

Portion ideas and pairings

One medium ear, or about a half cup of kernels.
Skip the butter and honey; use lime and chili instead.
Treat corn as the starch, and pick a different starch if you are also eating rice or potatoes.

Pairs well with: grilled chicken or fish, black beans in a salad, tomatoes and peppers.

Related foods

Sweet potato

cup, cubes: 27 g carbs

Potato

Potato medium: 37 g carbs

White rice, cooked

cup: 45 g carbs

Quinoa, cooked

cup: 39 g carbs

See all foods and the low glycemic foods list

Frequently asked questions

Is popcorn the same as sweet corn?

No. Popcorn is a whole grain, dried and puffed, and is counted differently. See the popcorn page for portions.

How many carbs are in a medium ear of sweet corn?

About 19 g of carbohydrate, of which about 2 g is fiber, so roughly 17 g net carbs. Values are from USDA FoodData Central for 102 g and are estimates; brands and sizes vary.

Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.

Sources

Last reviewed: October 22, 2026 by the Diabetes Blogs editorial team. Information only, not medical advice.