For a healthy adult without diabetes, blood sugar should stay between 60 and 100 mg/dL before meals and below 140 mg/dL after eating. These numbers shift depending on your age, whether you’re pregnant, and whether you’re managing a condition like diabetes. Here’s a closer look at what each range means and why it matters.
Normal Fasting Blood Sugar
A fasting blood sugar level, taken after at least eight hours without food, falls below 100 mg/dL in a healthy person. Most people without diabetes or prediabetes maintain overnight and pre-meal glucose between 60 and 100 mg/dL. Once fasting levels creep into the 100 to 125 mg/dL range, that’s considered prediabetes. A fasting reading of 126 mg/dL or higher on two separate tests indicates diabetes.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal, peaking about one to two hours later. In someone without diabetes, that peak typically stays below 140 mg/dL and then drops back down. If you’re managing diabetes, your care team may give you a more specific post-meal target, but 140 mg/dL at the two-hour mark is the general healthy benchmark.
Most people never notice these fluctuations because the body releases insulin quickly enough to keep glucose in check. Problems arise when the body can’t produce enough insulin or can’t use it efficiently, causing blood sugar to stay elevated for longer stretches.
The A1C Test: Your Three-Month Average
While a finger stick or lab draw gives you a snapshot, 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. The standard ranges are:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
An A1C of 5.7% corresponds roughly to an average blood sugar of about 117 mg/dL, while 6.5% corresponds to roughly 140 mg/dL. This test is useful because it smooths out the daily ups and downs and shows whether your blood sugar has been running high over time, even if a single fasting test looks fine.
When Blood Sugar Drops Too Low
Blood sugar below 70 mg/dL is considered low, a condition called hypoglycemia. Symptoms include shakiness, sweating, confusion, irritability, and a fast heartbeat. Below 54 mg/dL is classified as severely low and can become dangerous, potentially causing seizures or loss of consciousness.
Hypoglycemia is most common in people taking insulin or certain diabetes medications, but it can occasionally happen to anyone after prolonged fasting, intense exercise, or heavy alcohol intake. The standard response is to eat or drink about 15 grams of fast-acting carbohydrates (a few glucose tablets, half a cup of juice) and recheck after 15 minutes.
When Blood Sugar Runs Too High
On the other end, symptoms of high blood sugar typically don’t appear until levels exceed 180 to 200 mg/dL. At that point, you might notice frequent urination, increased thirst, blurred vision, and unusual fatigue. The tricky part is that blood sugar can sit in the 140 to 180 mg/dL range for months or years without obvious symptoms, quietly increasing the risk of complications. That’s why routine testing matters even when you feel fine.
Targets During Pregnancy
Pregnancy tightens the acceptable range because elevated blood sugar can affect both the mother and the developing baby. The American Diabetes Association and the American College of Obstetricians and Gynecologists recommend:
- Fasting: below 95 mg/dL
- One hour after a meal: below 140 mg/dL
- Two hours after a meal: below 120 mg/dL
These targets apply whether you had diabetes before becoming pregnant or developed gestational diabetes during pregnancy. The narrower range reflects how sensitive fetal development is to glucose levels, particularly during the second and third trimesters.
Targets for Children With Diabetes
Children and adolescents managing type 1 diabetes have slightly different goals than adults. Guidelines recommend pre-meal blood sugar between 90 and 130 mg/dL and bedtime readings between 90 and 150 mg/dL, with an A1C target generally below 7%. For younger children who can’t easily recognize or communicate symptoms of low blood sugar, a slightly higher A1C target of 7.5% is often more appropriate to reduce the risk of dangerous lows.
Why Targets Shift for Older Adults
For older adults with diabetes, especially those over 80 or living with other serious health conditions, guidelines generally relax blood sugar targets. An A1C of 7 to 7.5% is typical for otherwise healthy older adults, while 7 to 8% may be more suitable for those who are frail or managing conditions like dementia or heart failure.
The reason is straightforward: the risks of low blood sugar become more dangerous with age. Older adults are more likely to experience hypoglycemia without recognizing it, and a severe low can trigger falls, cardiovascular events, or worsening cognitive function. For someone with limited life expectancy, the goal shifts from hitting a specific number to simply preventing symptoms and maintaining quality of life.
Time in Range for Continuous Monitors
If you wear a continuous glucose monitor (CGM), you’ll encounter a metric called “time in range,” which tracks the percentage of the day your blood sugar stays within your target zone. For most people with type 1 or type 2 diabetes, the goal is to stay in range at least 70% of the time, roughly 17 out of 24 hours. Your specific range is usually set between 70 and 180 mg/dL, though your care team may adjust it based on your situation.
Time in range has become a popular complement to A1C because it captures the daily variability that A1C averages away. Two people can have the same A1C, but one might have steady glucose while the other swings wildly between highs and lows. The CGM data reveals those patterns in a way a quarterly blood test cannot.
Quick Reference by Category
- Healthy adult, fasting: 60 to 100 mg/dL
- Healthy adult, after meals: below 140 mg/dL
- Prediabetes, fasting: 100 to 125 mg/dL
- Diabetes diagnosis, fasting: 126 mg/dL or higher
- Low blood sugar: below 70 mg/dL
- Severely low: below 54 mg/dL
- Symptoms of high blood sugar typically start: above 180 to 200 mg/dL