A normal fasting blood sugar level is below 100 mg/dL (5.6 mmol/L). That single number is the most widely used benchmark, but “normal” actually shifts depending on when you last ate, whether you’re pregnant, and what type of test you’re looking at. Here’s a full breakdown of the ranges that matter.
Normal Fasting Blood Sugar
Fasting blood sugar is measured after you haven’t eaten for at least eight hours, typically first thing in the morning. The thresholds are straightforward:
- Normal: below 100 mg/dL (5.6 mmol/L)
- Prediabetes: 100 to 125 mg/dL (5.6 to 6.9 mmol/L)
- Diabetes: 126 mg/dL (7.0 mmol/L) or higher
That 100 to 125 mg/dL zone is sometimes called impaired fasting glucose. It means your body is starting to have trouble processing sugar efficiently, but hasn’t crossed into diabetes. Many people sit in this range for years without knowing it, which is why routine bloodwork matters.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal, peaks around one to two hours later, and then gradually returns to baseline. In a healthy person, it stays below 140 mg/dL (7.8 mmol/L) at the two-hour mark. This is the cutoff used in the oral glucose tolerance test, where you drink a standardized sugar solution and have your blood drawn two hours later.
If your two-hour result lands between 140 and 199 mg/dL, that signals prediabetes (also called impaired glucose tolerance). A result of 200 mg/dL or higher points to diabetes. In everyday life, you won’t hit these numbers precisely because meals vary in size and composition, but the 140 mg/dL threshold gives you a useful reference point if you’re checking at home with a glucose meter.
HbA1c: Your Three-Month Average
The HbA1c test (often just called A1c) measures the percentage of your red blood cells that have sugar attached to them. Because red blood cells live about three months, the result reflects your average blood sugar over that window rather than a single snapshot. The ranges, set by the American Diabetes Association and confirmed by the CDC, are:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
A1c is useful because it doesn’t require fasting and isn’t affected by what you ate yesterday. It can be less accurate, though, if you have certain blood conditions that change how long your red blood cells survive, like sickle cell trait or significant anemia.
Normal Ranges During Pregnancy
Pregnancy changes how your body handles sugar. Most pregnant women are screened between 24 and 28 weeks with a glucose challenge test: you drink a sugary liquid and have your blood drawn one hour later. A result below 140 mg/dL is considered normal. Some clinics use a lower cutoff of 130 mg/dL.
If your one-hour result is between 140 and 189 mg/dL, you’ll move on to a longer, three-hour glucose tolerance test. During that test, normal results are 180 mg/dL or lower at the one-hour mark and 155 mg/dL or lower at two hours. A one-hour result of 190 mg/dL or higher on the initial screen is enough to diagnose gestational diabetes on its own, without the follow-up test.
Women diagnosed with gestational diabetes typically monitor blood sugar at home before breakfast and after meals, with tighter targets than non-pregnant adults use.
Ranges for Children
Healthy children without diabetes follow the same general fasting threshold as adults: below 100 mg/dL. But for children who already have diabetes and are managing their blood sugar day to day, the targets are intentionally wider to account for unpredictable eating patterns and the risks of blood sugar dropping too low.
The American Diabetes Association sets these age-adjusted goals for children with diabetes:
- Ages 0 to 6: blood sugar goal of 100 to 200 mg/dL, A1c under 8.5%
- Ages 6 to 12: blood sugar goal of 90 to 180 mg/dL, A1c under 8%
These are looser than adult targets because low blood sugar episodes are especially dangerous in young children, who may not recognize or communicate symptoms.
What Continuous Glucose Monitors Show
If you wear a continuous glucose monitor (CGM), you’ll see your levels fluctuate throughout the day in real time. The key metric is called “time in range,” which tells you what percentage of the day your blood sugar stays within a target window. For most adults with diabetes, that window is 70 to 180 mg/dL, and the goal is to spend at least 70% of the day (roughly 17 hours) within it.
The full breakdown of CGM targets for most adults with type 1 or type 2 diabetes looks like this:
- In range (70 to 180 mg/dL): at least 70% of the day
- Mildly low (54 to 69 mg/dL): less than 4% of the day
- Very low (below 54 mg/dL): less than 1% of the day
- High (181 to 250 mg/dL): less than 25% of the day
People without diabetes who wear CGMs out of curiosity tend to see their readings stay between roughly 70 and 120 mg/dL for most of the day, with brief spikes after meals that rarely exceed 140.
Converting Between mg/dL and mmol/L
Blood sugar is reported in mg/dL in the United States and in mmol/L in most other countries. The conversion is simple: divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL. So a fasting level of 100 mg/dL equals 5.6 mmol/L, and the diabetes threshold of 126 mg/dL equals 7.0 mmol/L.
What the Numbers Mean in Practice
A single reading outside the normal range doesn’t automatically mean something is wrong. Stress, illness, poor sleep, and even intense exercise can temporarily push blood sugar higher. Diagnosis typically requires two abnormal results on separate occasions, or one clearly elevated result combined with symptoms like excessive thirst, frequent urination, and unexplained weight loss.
If your fasting blood sugar sits in the prediabetes range (100 to 125 mg/dL) or your A1c is between 5.7% and 6.4%, the trajectory is not locked in. Prediabetes is the stage where lifestyle changes, particularly losing 5 to 7% of body weight and getting regular physical activity, have the strongest evidence for preventing progression to type 2 diabetes. Catching it at this stage is exactly the point of knowing what “normal” looks like.