What are normal blood sugar levels for adults?

Fasting, post-meal and HbA1c ranges considered normal, prediabetic and diabetic — in mg/dL and mmol/L.

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 June 1, 2026 4 min readEditorial policy

Knowing what "normal" looks like is the first step toward managing blood sugar. Here are the numbers most clinicians use.

Fasting blood sugar (no food for 8+ hours)

Normal: under 100 mg/dL (5.6 mmol/L)
Prediabetes: 100–125 mg/dL (5.6–6.9 mmol/L)
Diabetes: 126 mg/dL (7.0 mmol/L) or higher on two separate tests

2 hours after a meal

Normal: under 140 mg/dL (7.8 mmol/L)
Prediabetes: 140–199 mg/dL (7.8–11.0 mmol/L)
Diabetes: 200 mg/dL (11.1 mmol/L) or higher

HbA1c (3-month average)

Normal: below 5.7%
Prediabetes: 5.7%–6.4%
Diabetes: 6.5% or higher

Why post-meal numbers matter most

Fasting glucose is only one snapshot. Post-meal spikes are what damage blood vessels over time. A CGM or finger-stick test 1–2 hours after eating gives you a far better picture of your real glycemic health.

When to retest

If a single reading is off, retest before panicking. Stress, illness, dehydration, poor sleep and even strong coffee can shift glucose by 20–40 mg/dL temporarily.

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.