What is a normal blood sugar level?
On this page
Under 100 mg/dL (5.6 mmol/L) fasting, under 140 (7.8) two hours after the lab’s glucose drink, and an A1c under 5.7% (39 mmol/mol). Those lines are the same at every adult age. At any other time of day there’s no official line, and a number from a meter or a sensor can’t tell you where you stand on its own.
What we’d do
Know two lab numbers, a fasting glucose and an A1c, and ignore random readings until you have them. If both are normal, test again every 3 years from age 35. If either one is in the prediabetes range, that’s the number to work on.
Why “normal” is confusing
There are four different tests, two units, and now a sensor on people’s arms that shows a number every few minutes. Each test has its own lines, and an ordinary meal has no line at all. That’s how people end up holding a sensor peak after pasta up against the fasting line and panicking.
The US lines
These are the lines in the American Diabetes Association’s 2026 standards.
| Test | Normal | Prediabetes range | Diabetes range |
|---|---|---|---|
| Fasting (8 hours, no calories) | under 100 mg/dL (5.6 mmol/L) | 100 to 125 (5.6 to 6.9) | 126 (7.0) or more |
| 2 hours after a 75 g glucose drink | under 140 (7.8) | 140 to 199 (7.8 to 11.0) | 200 (11.1) or more |
| A1c | under 5.7% (39 mmol/mol) | 5.7 to 6.4% (39 to 47) | 6.5% (48) or more |
| Any time | no line | no line | 200 (11.1) or more with symptoms |
Under 70 (3.9) is low at any time. A diagnosis takes two abnormal results, from two tests or the same test twice, unless the number is clearly high. To convert mg/dL to mmol/L, divide by 18.
How little sugar is in your blood
All the sugar in the blood of a 154 pound (70 kg) adult adds up to about 4 grams. That’s one teaspoon. A 12-ounce can of cola has 39 grams, almost 10 teaspoons, so a single can holds about ten times what’s in your whole bloodstream at once.
Your body keeps that teaspoon steady the way a thermostat keeps a room steady. When sugar comes in from a meal, insulin moves it out of the blood and into storage. About 80% of the sugar insulin moves goes into your muscles. Between meals and overnight, your liver feeds sugar back in.
On a sensor, healthy people stay inside a narrow band. In 153 healthy people aged 7 to 80 wearing a blinded Dexcom G6, the average was 98 to 99 mg/dL, 104 in people over 60, and they spent 96% of the day between 70 and 140.
Which number to trust
A lab test decides a band. A finger-stick meter or a home A1c kit can only tell you to get a lab test. A sensor runs higher than your blood and can’t diagnose anything, but it’s good for comparing your own meals (more in how accurate are glucose sensors).
Pregnancy uses tighter numbers, so take any number to your midwife or doctor. If you take insulin or a sulfonylurea, your targets come from your prescriber.
Put your own number into the checker to see its band in both units and the next step, or print the blood sugar chart.
6 sources
- American Diabetes Association, Standards of Care in Diabetes 2026, section 2, Diagnosis and Classification of Diabetespmc.ncbi.nlm.nih.gov
- Wasserman DH, Four grams of glucose, American Journal of Physiology, Endocrinology and Metabolism, 2009pmc.ncbi.nlm.nih.gov
- Harvard T.H. Chan School of Public Health, Added sugar in the diet, The Nutrition Sourcenutritionsource.hsph.harvard.edu
- DeFronzo RA and Tripathy D, Skeletal muscle insulin resistance is the primary defect in type 2 diabetes, Diabetes Care, 2009pmc.ncbi.nlm.nih.gov
- Shah VN and others, Continuous glucose monitoring profiles in healthy nondiabetic participants: a multicenter prospective study, Journal of Clinical Endocrinology and Metabolism, 2019pmc.ncbi.nlm.nih.gov
- American Diabetes Association, Hypoglycemia (low blood glucose)diabetes.org
