Most potatoes test high on the glycemic index, commonly in the 70s and 80s, though the number swings widely depending on variety and how they're cooked. Potatoes aren't off-limits for diabetes, but portion size, cooking method, and what ends up on top of them matter more than the potato itself.
The numbers
Most potatoes test high GI, commonly in the 70s and 80s, and the 2021 international GI tables found most potato varieties land in the high range (Atkinson et al., American Journal of Clinical Nutrition, 2021). But that typical range hides a lot of variation, with tested values running from the 50s to over 100 (Sagili et al., Foods, 2022):
| Preparation | Typical GI | Why |
|---|---|---|
| Boiled or baked | High (roughly 70s to 80s) | Similar range whether cooked in water or the oven; variety moves the number more than method does |
| Mashed or instant mashed | High (often the highest of the group) | Breaking down the structure by mashing speeds up digestion |
| Fried (french fries) | Medium (about 64 in testing), plus a separate risk factor | Frying itself doesn't drastically change the GI, but the added fat and processing are linked to meaningfully higher diabetes risk independent of the glycemic number (Muraki et al., Diabetes Care, 2016) |
| Boiled, then cooled (potato salad) | Meaningfully lower | Cooling raises resistant starch, the same mechanism covered on our white rice page |
A typical medium baked potato (about 173 grams) has roughly 33 grams of available carbohydrate (USDA FoodData Central). At a GI in the 70s or 80s, that works out to a glycemic load of roughly 23 to 29 (GI × 33 ÷ 100), high for one potato on its own. See how that compares with rice, pasta, and bread in our GI vs. GL chart of common foods.
Cooling potatoes lowers the effective impact
Cooking and then cooling a potato, the same idea behind potato salad, converts some of its starch into resistant starch, a form your body digests more slowly and absorbs less completely. Harvard's Nutrition Source specifically notes that boiling and then cooling potatoes increases resistant starch and "will tend to reduce the glycemic load." It's the same mechanism discussed on our white rice page for cooled rice, and it applies the same way here: a cold potato salad behaves somewhat differently in your body than the same potato eaten hot.
A smaller portion (closer to the size of your fist) paired with protein and non-starchy vegetables blunts the impact more than any single cooking trick. Leaving the skin on adds fiber. Swapping half the potato for cauliflower mash, or choosing a boiled-and-cooled preparation over hot mashed potatoes, are both reasonable ways to soften the response without cutting potatoes out entirely. See our sweet corn page for another starchy side where the reputation is worse than the real number.
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Potato GI depends heavily on variety and prep, more than most foods on this list. Glycemic Genius reads the nutrition facts panel on a specific product and returns an AI estimate of GI and glycemic load on the spot, rather than relying on a single category average. See our comparison of glycemic index apps for more.