What is the glycemic load and why it matters more than the glycemic index

The glycemic index ranks foods, but the glycemic load tells you how they'll actually affect your blood sugar. Here's the difference, with examples.

Written by

Carb Lens Editorial

Nutrition writers & product team

Medically reviewed by

Dr. Alicia Nguyen, RD, CDCES

Registered Dietitian · Certified Diabetes Care & Education Specialist · 12+ years clinical experience

Published May 22, 2026 4 min readEditorial policy

Glycemic index (GI) is one of the most misunderstood numbers in nutrition. Watermelon has a GI of 80 — higher than table sugar — yet eating a normal slice barely moves blood glucose. The reason is glycemic load.

Glycemic index vs glycemic load

**Glycemic index** ranks how quickly 50g of *carbohydrate* from a food raises blood sugar compared to pure glucose.
**Glycemic load** is the GI multiplied by the *grams of carbs in an actual serving*, divided by 100.

In other words: GI tells you what kind of carb it is. GL tells you how much you're actually eating.

A worked example

Watermelon: - GI: 80 - Carbs per 120g serving: 9g - GL: (80 × 9) / 100 = 7.2 → low

Bagel: - GI: 72 - Carbs per 100g serving: 50g - GL: (72 × 50) / 100 = 36 → very high

The bagel will spike blood sugar much harder than the watermelon, even though the GI numbers are close.

How to use glycemic load in practice

GL of 1-10: low, safe for most meals
GL of 11-19: moderate, pair with protein and fat
GL of 20+: high, eat sparingly or split across the day

Why Carb Lens reports both

The scanner estimates glycemic load for every meal because it's a better real-world predictor than GI alone. The "blood sugar impact" tag (low / moderate / high) on each scan combines GL with portion size, fiber and protein to give a single, glanceable answer.

About the author

Carb Lens Editorial — Nutrition writers & product team. The Carb Lens editorial team writes practical, source-checked guides on carbs, blood sugar, and everyday nutrition. Every article is drafted by our writers and cross-referenced against USDA FoodData Central and peer-reviewed clinical guidelines.

How we source and review this article

Nutrition figures come from the USDA FoodData Central database. Blood-sugar and glycemic-load framing follows guidance from the American Diabetes Association and World Health Organization healthy-diet recommendations. Every article is medically reviewed by Dr. Alicia Nguyen, RD, CDCES before publishing and re-checked on a rolling basis. See our full editorial & medical review policy.

This article is for general information and is not a substitute for medical advice. If you're managing diabetes or another condition, always defer to your care team.