Fasting Blood Sugar: Normal Range and Morning Readings
A fasting blood sugar of 99 mg/dL (5.5 mmol/L) or below is under the prediabetes range. 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is the prediabetes range and 126 mg/dL (7.0 mmol/L) or higher is the diabetes range. One result is not a diagnosis; a clinician confirms it.
| Fasting plasma glucose (mg/dLmmol/L) | ADA / NIDDK category |
|---|---|
| ≤ 99≤ 5.5 | Under the prediabetes range |
| 100–1255.6–6.9 | Prediabetes range (impaired fasting glucose) |
| ≥ 126≥ 7.0 | Diabetes range, confirmed by a repeat or second test unless symptoms are clear |
What “fasting” means
The ADA defines fasting as no calories for at least 8 hours, and the NIDDK adds that small sips of water are fine. The lab test is usually drawn in the morning for that reason. A reading you take at home on waking is a fasting reading only if you have not eaten or had a caloric drink overnight.
Fasting blood sugar for a person with diabetes
For many nonpregnant adults with diabetes, the ADA gives a before-meal target of 80 to 130 mg/dL (4.4 to 7.2 mmol/L). A fasting reading is a before-meal reading. For older adults the ADA gives other ranges depending on health: 80 to 130 for healthy older adults, 90 to 150 for complex or intermediate health, and 100 to 180 for very complex or poor health (Table 13.2). See the full blood sugar chart.
Blood sugar in the morning
Morning is when many people see their highest fasting numbers, and when puzzled readings are common. Some possibilities:
- The dawn phenomenon. In the early hours the body releases hormones that raise glucose. In people with diabetes the rise may not be offset. See the dawn phenomenon page.
- A rebound after a low. A low overnight can trigger hormones that raise glucose by morning. Clinicians sometimes call this the Somogyi effect, though how common it is remains debated. Only an overnight check or CGM tells the two apart.
- Evening food and activity. A late, large meal, alcohol or a very still evening can shape the morning number.
- Illness, stress, poor sleep or a new medicine. These can raise it too.
- Medicine timing. Your care team may change this. Please do not adjust doses yourself.
If you see a persistent pattern, record a week of morning readings in the blood sugar log and show it to your care team. If you wake with symptoms of a low, check right away and follow the rule of 15.
Fasting glucose and A1C
Fasting glucose is a snapshot of one morning. A1C averages about three months. The ADA recognizes both for diagnosis, and they sometimes disagree, which is one reason a second test is used. The A1C calculator turns A1C into an average glucose so you can compare.
Frequently asked questions
What is a normal fasting blood sugar?
The NIDDK lists a fasting plasma glucose of 99 mg/dL (5.5 mmol/L) or below as under the prediabetes range, 100 to 125 mg/dL (5.6 to 6.9 mmol/L) as the prediabetes range, and 126 mg/dL (7.0 mmol/L) or higher as the diabetes range. A clinician confirms a diagnosis with a second result.
What counts as fasting?
The ADA defines fasting as no calories for at least 8 hours. The NIDDK says small sips of water are fine. Coffee with milk, juice or gum with sugar breaks the fast.
What should my fasting blood sugar be if I have diabetes?
For many nonpregnant adults, the ADA gives a before-meal target of 80 to 130 mg/dL (4.4 to 7.2 mmol/L), and a fasting reading falls under that. Older adults with complex health can have looser goals. Your care team sets yours.
Why is my morning blood sugar high?
Common reasons include the dawn phenomenon, a natural early-morning hormone rise, a late or large evening meal, illness, or medicine timing. Sometimes a low overnight is followed by a high. A CGM or a check in the night can show which, and your care team can interpret it.
Is a fasting reading from a home meter a diagnosis?
No. Diagnosis uses a laboratory plasma glucose test. Home meters are screened to be close but are not the same, and meters can be off by some percent.
Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.
Sources
- NIDDK: Diagnosis of Diabetes and Prediabetes
- ADA Standards of Care in Diabetes—2026, Section 2: Diagnosis and Classification
- ADA Standards of Care in Diabetes—2026, Section 6: Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises
- ADA Standards of Care in Diabetes—2026, Section 13: Older Adults
- Dawn Phenomenon. StatPearls, NCBI Bookshelf
Last reviewed: by the Diabetes Blogs editorial team. Information only, not medical advice.
