A regular (normal) blood sugar level depends on when you last ate, but the key number most people want to know is fasting blood glucose: below 100 mg/dL. After meals, a normal reading stays below 140 mg/dL. These thresholds separate healthy blood sugar from prediabetes and diabetes, and understanding where you fall can help you make sense of lab results or home meter readings.
Fasting Blood Sugar: The Baseline Number
Fasting blood sugar is measured after you haven’t eaten or had anything to drink (besides water) for at least eight hours. It’s the most common screening test and the number your doctor is most likely to check at a routine physical.
- Normal: 99 mg/dL or below
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
If your fasting level comes back in the prediabetes range, it means your body is starting to have trouble processing sugar efficiently, but the damage is not yet permanent. A result of 126 mg/dL or above, confirmed on a second test, meets the diagnostic threshold for type 2 diabetes.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal as your body breaks down carbohydrates into glucose. In a healthy person, insulin kicks in quickly and brings that spike back down within a couple of hours. A formal test called an oral glucose tolerance test measures this by having you drink a standardized sugary liquid and checking your blood two hours later.
- Normal: below 140 mg/dL at the two-hour mark
- Prediabetes: 140 to 199 mg/dL
- Diabetes: 200 mg/dL or higher
If you’re checking at home with a glucose meter, your reading one to two hours after starting a meal should generally stay under 140 mg/dL. A post-meal spike that regularly exceeds that range can signal early insulin resistance even when your fasting numbers still look fine.
A1C: Your Three-Month Average
While a fasting test captures a single snapshot, the A1C test reflects your average blood sugar over the previous two to three months. It works by measuring the percentage of hemoglobin (a protein in red blood cells) that has glucose attached to it. The higher your blood sugar has been running, the higher the percentage.
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
Within the prediabetes range, risk isn’t flat. Someone at 6.3% is considerably closer to developing diabetes than someone at 5.8%. The A1C is especially useful because it doesn’t require fasting, can be drawn at any time of day, and isn’t thrown off by what you ate yesterday.
When Blood Sugar Drops Too Low
Most conversations focus on high blood sugar, but low blood sugar (hypoglycemia) matters too, especially for people taking insulin or certain diabetes medications. Blood sugar below 70 mg/dL is considered low. Symptoms at this level typically include shakiness, sweating, dizziness, irritability, and sudden hunger.
Severe hypoglycemia, defined as blood sugar below 54 mg/dL, is a medical emergency. At that level, you can experience confusion, blurred vision, seizures, or loss of consciousness. For people without diabetes, blood sugar rarely drops this low unless there’s an underlying condition like an insulin-producing tumor or prolonged fasting combined with intense exercise.
Normal Ranges for Children
Children’s blood sugar ranges shift as they grow. Newborns naturally run lower, with a normal range of about 30 to 60 mg/dL. Infants settle into a range of roughly 40 to 90 mg/dL. By age two, children’s values closely resemble adult ranges at about 60 to 100 mg/dL. These lower numbers in very young children are normal and don’t indicate a problem on their own.
Blood Sugar During Pregnancy
Pregnancy changes how the body handles insulin, so screening for gestational diabetes is standard between 24 and 28 weeks. The initial screening involves drinking a sugary solution and having blood drawn one hour later. A result below 140 mg/dL is considered within the standard range. A reading of 190 mg/dL or above on this first test typically means gestational diabetes without further testing needed.
If the first result falls between 140 and 189 mg/dL, a longer follow-up test is done. You fast overnight, drink a higher-sugar solution, and have blood drawn every hour for three hours. If two or more of those readings come in higher than expected, that confirms gestational diabetes. Blood sugar targets during a gestational diabetes pregnancy are tighter than usual to protect both mother and baby.
Converting Between mg/dL and mmol/L
If you live in the United States, your results come in mg/dL. Most other countries, including the UK, Canada, and Australia, use mmol/L. The conversion is straightforward: divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL.
So a fasting level of 99 mg/dL equals about 5.5 mmol/L, and the diabetes threshold of 126 mg/dL equals 7.0 mmol/L. Keeping this conversion in mind is helpful if you’re reading health information from international sources or using a meter calibrated in the other unit.
What Prediabetes Actually Means
About one in three American adults has prediabetes, and most don’t know it. The label covers a fasting glucose of 100 to 125 mg/dL, a two-hour glucose tolerance result of 140 to 199 mg/dL, or an A1C between 5.7% and 6.4%. Any one of these qualifies.
Prediabetes isn’t a guarantee that you’ll develop type 2 diabetes. It’s a warning sign that your body is losing its ability to keep blood sugar in check. Weight loss of even 5% to 7% of body weight, combined with regular physical activity, has been shown to cut the risk of progressing to diabetes nearly in half. That makes the prediabetes range one of the most actionable results you can get on a blood test: it’s early enough that lifestyle changes can genuinely reverse the trend.