A normal fasting blood sugar level is below 100 mg/dL (5.6 mmol/L). That’s the number most people encounter first, since fasting glucose is the most common screening test. But “normal” shifts depending on when you last ate, whether you’re pregnant, and how the measurement is taken. Here’s what each number means.
Normal Fasting Blood Sugar
Fasting blood sugar is measured after you haven’t eaten for at least 8 hours, typically first thing in the morning. A reading below 100 mg/dL is considered normal. Between 100 and 125 mg/dL falls into the prediabetes range, and 126 mg/dL or higher on two separate tests indicates diabetes.
If you’re wearing a continuous glucose monitor (CGM), your fasting number might look slightly different from a lab draw, but the thresholds are the same. In a large study of over 4,800 people without diabetes, the average fasting glucose was 91 mg/dL, which gives you a sense of where most healthy adults land. Waking up in the low 80s to mid-90s is typical.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal and then comes back down. In someone without diabetes, it should return to below 140 mg/dL within two hours of eating. Most healthy people peak somewhere between 30 and 60 minutes after a meal and settle back near their baseline well before the two-hour mark.
During pregnancy, the targets are tighter. Doctors typically recommend blood sugar stay below 140 mg/dL one hour after eating and below 120 mg/dL at the two-hour mark. Fasting levels in pregnancy should stay below 95 mg/dL. These lower thresholds exist because even mildly elevated blood sugar during pregnancy can affect the baby’s growth.
The A1C Test: A Longer View
While fasting and post-meal readings capture a single moment, the A1C test reflects your average blood sugar over the past two to three months. It measures the percentage of your red blood cells that have sugar attached to them. 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 above
An A1C of 5.7% corresponds roughly to an average blood sugar of about 117 mg/dL. This test is useful because it isn’t thrown off by what you ate yesterday or whether you were stressed during the blood draw. It’s the number doctors rely on for diagnosis and for tracking how well blood sugar is being managed over time.
What Continuous Monitors Show in Healthy People
Continuous glucose monitors have given researchers a much richer picture of what “normal” actually looks like throughout the day. Blood sugar doesn’t sit at one steady number. It rises and dips constantly in response to meals, exercise, stress, and sleep.
In a study of nearly 5,000 non-diabetic adults wearing monitors for two to four days, participants spent about 91% of their time in the 70 to 140 mg/dL range. That means even healthy people drift above 140 or below 70 for portions of the day. Brief spikes after a carb-heavy meal or a small dip during exercise are normal and not a cause for concern. The pattern matters more than any single reading.
When Blood Sugar Drops Too Low
Blood sugar below 70 mg/dL is considered low, a condition called hypoglycemia. Below 54 mg/dL is classified as severely low and can become dangerous. Symptoms of low blood sugar include shakiness, sweating, confusion, a rapid heartbeat, and irritability. In people without diabetes, true hypoglycemia is uncommon, though some people experience mild dips that feel unpleasant after skipping meals or intense exercise.
For people taking insulin or certain diabetes medications, low blood sugar is a more serious and frequent risk. Eating or drinking something with fast-acting sugar (juice, glucose tablets, regular soda) raises blood sugar within about 15 minutes.
Normal Ranges for Children
Children’s normal blood sugar ranges shift with age, particularly in the first two years of life. Newborns have naturally lower blood sugar, with a normal range of 30 to 60 mg/dL. Infants settle into a range of 40 to 90 mg/dL, and by age two, children reach an adult-like range of 60 to 100 mg/dL. These lower numbers in newborns are expected and reflect normal metabolism in the first days of life, not a problem that needs treatment unless levels drop unusually low or the baby shows symptoms.
Glucose Tolerance Test Results
If your fasting number or A1C is borderline, your doctor may order a glucose tolerance test. You’ll drink a sugary solution containing 75 grams of glucose, then have your blood drawn two hours later. A result below 140 mg/dL at the two-hour mark is normal. Between 140 and 199 mg/dL indicates prediabetes, and 200 mg/dL or above points to diabetes.
This test is especially useful for catching prediabetes that fasting glucose alone might miss. Some people have normal fasting numbers but struggle to clear sugar from their blood efficiently after a large glucose load. The tolerance test reveals that pattern.
What Affects Your Numbers
Several things can shift your blood sugar reading without meaning anything is wrong. Poor sleep, even a single bad night, can temporarily raise fasting glucose. Physical or emotional stress triggers hormones that push blood sugar up. Dehydration concentrates your blood and can nudge readings slightly higher. Coffee, even black, causes a small glucose bump in some people.
Illness has a particularly strong effect. Infections, colds, and even minor viruses can raise blood sugar noticeably for days. If you get an unexpectedly high reading while sick, that alone doesn’t mean you have diabetes. Retesting when you’ve recovered gives a more accurate picture.
Time of day matters too. Many people experience a “dawn phenomenon” where blood sugar rises in the early morning hours due to a natural surge of hormones that prepare your body for waking. This can make a 6 a.m. fasting reading a few points higher than a reading taken at midnight.