A normal fasting blood sugar level is between 70 and 99 mg/dL (3.9 to 5.5 mmol/L) for adults without diabetes. Numbers above that range signal either prediabetes or diabetes, depending on how high they go. But “normal” shifts based on when you last ate, your age, and whether you’re pregnant, so a single number doesn’t tell the whole story.
Fasting Blood Sugar Ranges
Fasting blood sugar is measured after at least eight hours without food, typically first thing in the morning. It’s the most common way doctors screen for blood sugar problems, and the cutoffs are straightforward:
- Normal: 70 to 99 mg/dL (3.9 to 5.5 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 on two or more tests
A single reading of 126 or above doesn’t automatically mean diabetes. Doctors confirm the diagnosis by repeating the test or combining it with other measures. Readings in the prediabetes range, though, are worth paying attention to. That 100 to 125 window means your body is already struggling to manage glucose efficiently, and lifestyle changes at this stage can often prevent progression to type 2 diabetes.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal, peaks around 60 to 90 minutes later, and then drops back down. The standard checkpoint is two hours after eating. For someone without diabetes, a reading below 140 mg/dL (7.8 mmol/L) at the two-hour mark is considered normal.
If you’re testing at home after meals and consistently seeing numbers above 140, that pattern can indicate your body isn’t clearing glucose from the bloodstream efficiently, even if your fasting numbers look fine. Some people with early insulin resistance show their first abnormal readings only after meals.
A1C: Your Three-Month Average
While a finger-stick test captures what’s happening right now, the A1C test reflects your average blood sugar over roughly three months. It measures the percentage of your red blood cells that have glucose attached to them, giving a much broader picture than any single reading.
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
For people already living with diabetes, the American Diabetes Association recommends keeping A1C below 7% in most cases. That target may be loosened for older adults or people with other serious health conditions, since pushing blood sugar too low can cause its own problems. Your specific goal depends on your overall health profile.
When Blood Sugar Drops Too Low
Blood sugar below 70 mg/dL (3.9 mmol/L) is considered low, a condition called hypoglycemia. For most people without diabetes, this is uncommon because the body has multiple backup systems to keep glucose from falling that far. It’s more of a concern for people taking insulin or certain diabetes medications that actively lower blood sugar.
Symptoms of low blood sugar include shakiness, sweating, a racing heart, irritability, and difficulty concentrating. Severe drops can cause confusion, blurred vision, or loss of consciousness. Eating or drinking something with fast-acting sugar (juice, glucose tablets, regular soda) typically brings levels back up within 15 minutes.
Ranges for Children
Children’s target ranges are slightly wider than adults’, reflecting the greater variability in how young bodies regulate glucose throughout the day:
- Under 5 years: 80 to 200 mg/dL
- Ages 5 to 11: 70 to 180 mg/dL
- Ages 12 and up: 70 to 150 mg/dL
These are general goals for children who are being monitored for diabetes. Healthy children without diabetes will naturally stay within narrower bounds most of the time, but pediatric targets are set wider to reduce the risk of dangerous lows, especially in very young kids who may not recognize or communicate symptoms.
Blood Sugar During Pregnancy
Pregnancy changes how your body processes glucose, and gestational diabetes develops in a significant number of pregnancies. Screening typically happens between weeks 24 and 28 using a glucose challenge test, where you drink a sugary solution and have your blood drawn one hour later.
On that initial screening, a result below 140 mg/dL is considered normal. A result between 140 and 189 mg/dL triggers a longer, three-hour follow-up test to confirm whether gestational diabetes is present. A reading of 190 mg/dL or higher on the first test usually indicates gestational diabetes without needing the follow-up. Some clinics use a lower screening cutoff of 130 mg/dL, so the threshold your provider uses may vary slightly.
mg/dL vs. mmol/L
Blood sugar is reported in two different units depending on where you live. The United States uses mg/dL (milligrams per deciliter), while most other countries, including the UK, Canada, and Australia, use mmol/L (millimoles per liter). If you need to convert between the two, divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL.
Some common reference points in both units:
- 70 mg/dL = 3.9 mmol/L (low blood sugar threshold)
- 100 mg/dL = 5.6 mmol/L (upper limit of normal fasting)
- 126 mg/dL = 7.0 mmol/L (diabetes fasting threshold)
- 140 mg/dL = 7.8 mmol/L (normal post-meal cutoff)
- 200 mg/dL = 11.1 mmol/L (high blood sugar)
What Can Temporarily Shift Your Numbers
Blood sugar isn’t static, even in people with perfectly healthy metabolisms. A number of everyday factors can push readings higher or lower without signaling an actual problem.
Sleep is a big one. Even a single night of poor sleep reduces how effectively your body uses insulin the next day. Stress has a similar effect: physical stress like a sunburn or illness triggers the release of hormones that raise blood sugar. Dehydration concentrates the glucose already in your bloodstream, making readings appear higher than they would if you were well-hydrated.
Caffeine can raise blood sugar in some people, even black coffee with no sweetener. Skipping breakfast has been shown to increase blood sugar after both lunch and dinner, likely because the body’s insulin response works less smoothly when the first meal is delayed. There’s also a natural hormonal surge in the early morning hours, sometimes called the dawn phenomenon, that pushes blood sugar up before you’ve eaten anything. This happens in everyone but is more pronounced in people with diabetes.
All of this means a single out-of-range reading isn’t necessarily cause for alarm. Patterns matter more than individual numbers. If you’re seeing consistently elevated readings across multiple tests and multiple days, that’s the signal worth acting on.