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Blood sugar levels chart (mg/dL)
Key takeaways
- A normal fasting blood sugar is below 100 mg/dL; 100–125 is the prediabetes range; 126+ is the diabetes range.
- A normal A1C is below 5.7%; 5.7–6.4% is prediabetes; 6.5% or higher is diabetes.
- Below 70 mg/dL is low blood sugar (hypoglycemia) and needs prompt attention.
- Diagnosis requires lab tests from a clinician — a single home reading can't diagnose diabetes.
In the United States, blood sugar (blood glucose) is measured in milligrams per deciliter (mg/dL). Many other countries use mmol/L; to convert, divide mg/dL by 18 (for example, 100 mg/dL ≈ 5.6 mmol/L).
Blood sugar chart: normal, prediabetes, and diabetes
These are the diagnostic ranges the American Diabetes Association (ADA) and CDC use for adults who are not pregnant.
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting blood sugar (8+ hours without food) | Below 100 mg/dL | 100–125 mg/dL | 126 mg/dL or higher |
| 2 hours after a glucose drink (OGTT) | Below 140 mg/dL | 140–199 mg/dL | 200 mg/dL or higher |
| A1C (average over ~3 months) | Below 5.7% | 5.7–6.4% | 6.5% or higher |
A diagnosis is made by a clinician, usually with repeat lab tests. Home meter readings are useful for tracking, but they don't replace lab testing.
Low blood sugar
The CDC describes blood sugar below 70 mg/dL as low (hypoglycemia). It can cause shakiness, sweating, a fast heartbeat, confusion, or irritability. People who use insulin or certain diabetes medicines are most at risk. Very low blood sugar is an emergency — call 911 if someone can't eat or drink safely or loses consciousness.
Targets if you already have diabetes
Daily targets are personal and should be set with your care team. The ADA's general targets for many nonpregnant adults with diabetes are about 80–130 mg/dL before meals and below 180 mg/dL one to two hours after the start of a meal. Your doctor may set different goals.
Why context makes readings useful
A number without context is hard to read. 140 mg/dL means something different before breakfast than an hour after a big lunch. Note when you measured — fasting, before a meal, after a meal, or at bedtime — and what you ate, how you slept, and whether you exercised.
Logging blood sugar in Cardivo
Cardivo lets you log readings from your meter or CGM in mg/dL in a few seconds, tag them fasting, after meal, or bedtime, and see them charted next to your heart rate, HRV, and mood. Cardivo does not measure blood sugar with the camera — no phone camera can. Export a PDF to bring to your next appointment.
This guide is general wellness education based on the public sources below. It is not medical advice, diagnosis, or treatment. Cardivo is not a medical device. If you think you are having a medical emergency, call 911.
Frequently asked questions
What is a normal blood sugar level?
For adults without diabetes, a normal fasting blood sugar is below 100 mg/dL, and a normal reading two hours after a glucose drink is below 140 mg/dL (ADA).
What blood sugar level is considered diabetes?
A fasting blood sugar of 126 mg/dL or higher, a 2-hour OGTT value of 200 mg/dL or higher, or an A1C of 6.5% or higher, confirmed by a clinician, is in the diabetes range.
What is a dangerous low blood sugar?
Below 70 mg/dL is considered low blood sugar. Treat it promptly as your care team advised, and call 911 for severe symptoms such as confusion, seizures, or loss of consciousness.
Can my iPhone measure blood sugar?
No. No phone camera can measure blood glucose. Apps like Cardivo let you log readings from a meter or continuous glucose monitor and see trends.