For an adult without diabetes, blood glucose is normally 70–99 mg/dL (3.9–5.5 mmol/L) after an overnight fast and below 140 mg/dL (7.8 mmol/L) two hours after a meal. A1C is below 5.7%. Fasting glucose of 100–125 mg/dL is prediabetes and 126 or above on two occasions is diabetes. For people already treated for diabetes, typical targets are 80–130 mg/dL before meals and below 180 mg/dL after — set individually. Normal ranges do not change meaningfully with age; treatment targets sometimes do.
The ranges
Blood glucose is expressed in milligrams per decilitre (mg/dL) in the United States and millimoles per litre (mmol/L) in the United Kingdom, Canada, Australia and most other countries. To convert, divide mg/dL by 18.
| When measured | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting (8+ hours) | 70–99 mg/dL (3.9–5.5 mmol/L) | 100–125 mg/dL (5.6–6.9 mmol/L) | 126 mg/dL (7.0 mmol/L) or higher |
| 2 hours after a meal or glucose drink | Below 140 mg/dL (7.8 mmol/L) | 140–199 mg/dL (7.8–11.0 mmol/L) | 200 mg/dL (11.1 mmol/L) or higher |
| Random, with symptoms | — | — | 200 mg/dL (11.1 mmol/L) or higher |
| A1C (3-month average) | Below 5.7% | 5.7–6.4% | 6.5% or higher |
A diagnosis of diabetes requires two abnormal results — either the same test on two days or two different tests — unless glucose is very high with clear symptoms.
What "normal" looks like across a day
In someone without diabetes, glucose rises after each meal, peaks at about 30–60 minutes, rarely exceeds 140 mg/dL, and returns to baseline within two to three hours. Overnight it settles into the 70s to 90s. Continuous glucose monitor studies of healthy adults show that most of the day is spent between 70 and 120 mg/dL, with brief excursions above that after larger carbohydrate meals.
Glucose is also slightly higher in the early morning, because of hormones released before waking (the dawn phenomenon), and slightly higher after the same meal in the evening than at breakfast.
Targets for people with diabetes
Once diabetes is diagnosed, the question shifts from "normal" to "target". Targets are looser than normal ranges, because the aim is to reduce complications without causing dangerous low blood sugar. A common set for non-pregnant adults:
- Before meals: 80–130 mg/dL (4.4–7.2 mmol/L)
- 1–2 hours after meals: below 180 mg/dL (10.0 mmol/L)
- A1C: below 7%
These are individualized. Younger people with a long life ahead and low hypoglycemia risk may be given tighter targets; older adults, those with other serious illnesses, or those who have had severe hypoglycemia may be given looser ones (A1C below 7.5–8%). Pregnancy has its own, tighter targets.
Does normal change with age?
The diagnostic thresholds do not. Insulin sensitivity does fall gradually with age, so average fasting glucose in a population drifts upward — but a fasting glucose of 110 is prediabetes at 70 just as it is at 30. What changes with age is the balance of benefit and harm in treatment, which is why targets for people with diabetes are sometimes relaxed in later life.
Children
Normal ranges for children are the same as for adults. Targets for children with diabetes are set by their care team and take account of the particular risks of hypoglycemia in the young.
How much does one reading mean?
Less than people assume. Fasting glucose varies by 10–15 mg/dL from day to day in the same person, and a single reading can be pushed up by poor sleep, illness, stress, a late meal or certain medications. A single result at the edge of a range is a reason to repeat the test, not a diagnosis. A1C, which averages three months, is more stable; the A1C guide explains its own blind spots.
Home glucose meters are accurate to within about 15% of a laboratory value, which is adequate for monitoring but not for diagnosis.
When a reading is a problem
- Above 125 fasting or 200 after eating, more than once: see a doctor for formal testing.
- Above 300 mg/dL (16.7 mmol/L) in someone with diabetes: contact your care team the same day. See high blood sugar for the emergency signs.
- Below 70 mg/dL (3.9 mmol/L) in someone on insulin or sulfonylureas: treat with 15 grams of fast-acting carbohydrate and re-check in 15 minutes.
- Below 54 mg/dL (3.0 mmol/L), or any low reading with confusion or inability to swallow: this is an emergency.
Where to go from here
If your fasting glucose is in the 100–125 range, read the prediabetes guide: this is the stage at which the most can be done. If you are seeing readings in the diabetes range, the type 2 diabetes guide explains what happens next. And if your numbers are normal but you have risk factors, the signs of insulin resistance are worth knowing.
Frequently asked questions
Is a fasting glucose of 95 normal?
Yes, it is within the normal range. Some clinicians note that values in the 90s carry a somewhat higher long-term risk of diabetes than values in the 80s, particularly if they have been rising, but 95 on its own is not a cause for concern.
What is a normal blood sugar for a 60-year-old?
The same as for a 30-year-old: fasting below 100 mg/dL. Normal ranges do not shift with age. What changes is that treatment targets for people who already have diabetes may be relaxed in older adults, particularly if they have other illnesses or are at risk of low blood sugar.
What blood sugar level is too low?
Below 70 mg/dL (3.9 mmol/L) is considered low (hypoglycemia) and, in someone on insulin or sulfonylureas, should be treated with fast-acting carbohydrate. Below 54 mg/dL (3.0 mmol/L) is clinically significant hypoglycemia. In people not on glucose-lowering medication, readings in the 60s during a long fast can be normal.
Is 200 after a meal dangerous?
A reading of 200 mg/dL (11.1 mmol/L) or above at any time, together with symptoms, meets the threshold for diabetes and should be checked by a doctor. It is not an emergency on its own, but it is not normal.
References
- NIDDK. Diabetes Tests & Diagnosis (2023). https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis
- American Diabetes Association, Diabetes Care 49(Suppl 1):S27–S49. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026 (2026). PubMed PMID 41358893. https://diabetesjournals.org/care/article/49/Supplement_1/S27/163926/2-Diagnosis-and-Classification-of-Diabetes
- NIDDK. The A1C Test & Diabetes (2023). https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test
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