A normal fasting blood sugar level is below 100 mg/dL, and a normal reading two hours after eating is below 140 mg/dL. These are the standard thresholds used to separate healthy blood sugar from the ranges that signal prediabetes or diabetes. But “normal” shifts depending on the type of test, whether you’re pregnant, and your age.
Fasting Blood Sugar
A fasting blood sugar test measures your glucose after at least eight hours without food, typically first thing in the morning. The three categories break down clearly:
- 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
A single high reading doesn’t automatically mean diabetes. The test is usually repeated on a separate day to confirm the result. That said, a fasting number consistently in the 100 to 125 range is worth paying attention to. Prediabetes affects roughly 1 in 3 American adults, and most don’t know they have it.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal as your body digests carbohydrates. In a healthy person, insulin brings it back down relatively quickly. The oral glucose tolerance test captures this process by measuring your blood sugar two hours after drinking a standardized sugary liquid.
- Normal: below 140 mg/dL (7.8 mmol/L)
- Prediabetes: 140 to 199 mg/dL (7.8 to 11.0 mmol/L)
- Diabetes: 200 mg/dL (11.1 mmol/L) or higher
If you’re checking your own blood sugar at home with a glucose meter, the two-hour post-meal window is the most useful comparison point. Most people without diabetes will see their levels peak around 30 to 60 minutes after eating and settle back below 140 within two hours. A reading that stays above 140 at the two-hour mark, especially after a typical (not unusually carb-heavy) meal, is a signal your body may be struggling to process glucose efficiently.
A1C: Your 2-to-3-Month Average
While a finger-stick test captures a single moment, the A1C test reflects your average blood sugar over the previous two to three months. It measures the percentage of hemoglobin in your 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
The A1C is particularly useful because it isn’t affected by what you ate the night before or whether you remembered to fast. It gives a broader picture of blood sugar control. An A1C of 5.7% corresponds roughly to an average blood sugar of about 117 mg/dL, while 6.5% corresponds to about 140 mg/dL. Some conditions, including certain types of anemia and sickle cell trait, can make A1C results less accurate.
Random Blood Sugar
A random blood sugar test can be taken at any time, regardless of when you last ate. There’s no defined “normal” cutoff for this test because levels naturally fluctuate throughout the day. However, a random reading of 200 mg/dL or higher, combined with symptoms like frequent urination, excessive thirst, or unexplained weight loss, is enough to diagnose diabetes without any additional testing.
Normal Ranges During Pregnancy
Pregnancy changes the way your body handles insulin, so the thresholds for gestational diabetes are stricter than standard adult cutoffs. Most pregnant people are screened between 24 and 28 weeks with a one-hour glucose challenge test. A result below 140 mg/dL is generally considered within the standard range, while a result of 190 mg/dL or higher indicates gestational diabetes.
If your one-hour result falls between 140 and 189, a longer three-hour test follows. The expected values for that test are:
- Fasting: 95 mg/dL or lower
- One hour: 180 mg/dL or lower
- Two hours: 155 mg/dL or lower
- Three hours: 140 mg/dL or lower
Notice that the fasting threshold during pregnancy (95 mg/dL) is lower than the standard adult cutoff of 100. Meeting or exceeding the threshold at two or more of these time points typically results in a gestational diabetes diagnosis.
How Numbers Differ for Children
Healthy blood sugar ranges for children depend on age. Newborns normally run much lower than adults, with levels between 30 and 60 mg/dL in the first days of life. Infants settle into a range of about 40 to 90 mg/dL, and by age two, the expected range (60 to 100 mg/dL) closely matches the adult standard. For older children and adolescents, the same adult thresholds of below 100 mg/dL fasting generally apply.
When Blood Sugar Drops Too Low
The conversation around “normal” glucose usually focuses on numbers that are too high, but low blood sugar (hypoglycemia) matters too. A reading below 70 mg/dL is considered low and can cause shakiness, sweating, confusion, and irritability. Below 54 mg/dL is classified as clinically significant hypoglycemia and requires immediate treatment with fast-acting carbohydrates like juice or glucose tablets. Severe low blood sugar can cause seizures or loss of consciousness and requires someone else’s help to treat.
Hypoglycemia is most common in people taking insulin or certain diabetes medications, but it can occasionally happen in people without diabetes after prolonged fasting, intense exercise, or heavy alcohol consumption.
Adjusted Targets for Older Adults
For adults 65 and older, especially those with other chronic conditions or cognitive impairment, treatment guidelines recommend more lenient blood sugar targets. The priority shifts from hitting perfect numbers to avoiding dangerous lows. Hypoglycemia in older adults carries a higher risk of falls, confusion, and hospitalization.
For older adults in hospitals or nursing facilities, recommended targets are 100 to 140 mg/dL fasting and 140 to 180 mg/dL after meals. These ranges are deliberately higher than what would be considered “normal” in a younger, healthy adult. The goal is stable, safe glucose levels rather than textbook perfection.
mg/dL vs. mmol/L
If you’re outside the United States, your meter likely reports blood sugar in mmol/L rather than mg/dL. To convert, divide the mg/dL number by 18. So a fasting level of 100 mg/dL equals about 5.6 mmol/L, and 140 mg/dL equals about 7.8 mmol/L. A quick reference: 90 mg/dL is 5.0 mmol/L, and 180 mg/dL is 10.0 mmol/L.
Both units measure the same thing. The numbers in this article use mg/dL (the U.S. standard), with mmol/L equivalents included where relevant. If you’re comparing results from different countries or devices, the conversion factor of 18 is all you need.