Normal fasting blood sugar is below 100 mg/dL. Levels between 100 and 125 mg/dL fall into the prediabetes range, and 126 mg/dL or higher on two separate tests means diabetes. Those three numbers are the foundation, but blood sugar ranges shift depending on when you last ate, whether you’re pregnant, and what type of test your doctor orders.
Fasting Blood Sugar Ranges
A fasting blood sugar test measures your glucose after at least eight hours without food, typically first thing in the morning. It’s the most common screening tool and the easiest to interpret:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher on two separate tests
That “two separate tests” part matters. A single high reading can happen because of stress, illness, or a bad night’s sleep. A diabetes diagnosis requires confirmation, either through a repeat fasting test or a different type of glucose test that also comes back in the diabetic range.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal and then comes back down as insulin moves glucose into your cells. In people without diabetes, that post-meal peak typically stays below 140 mg/dL about two hours after eating. A large carb-heavy meal might push it slightly higher for a short time, but it settles back quickly.
For people managing diabetes, the general target is to stay below 180 mg/dL two hours after the start of a meal. That ceiling is higher than what a non-diabetic body produces because achieving tighter control with medication or insulin can increase the risk of blood sugar dropping too low. Your doctor may set a more specific target based on your situation, but 180 mg/dL is the widely used benchmark.
A1C: Your Two-to-Three-Month Average
The A1C test doesn’t capture a single moment. It measures the percentage of your red blood cells that have glucose attached to them, which reflects your average blood sugar over roughly the past two to three months. The ranges mirror the fasting categories but use percentages instead of mg/dL:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
A1C is especially useful because it isn’t affected by what you ate yesterday or whether you fasted before the blood draw. It shows the bigger picture. For people already diagnosed with diabetes, most treatment plans aim to keep A1C below 7%, though some individuals using newer technology like continuous glucose monitors and automated insulin delivery systems can safely target 6.5% or lower.
Blood Sugar Ranges During Pregnancy
Pregnancy changes how your body processes glucose. Hormones from the placenta can make your cells more resistant to insulin, which is why most pregnant people are screened for gestational diabetes between 24 and 28 weeks. The screening is a two-step process.
First, you drink a sugary solution and have your blood drawn one hour later. If your result is above a screening threshold (typically 135 or 140 mg/dL, depending on the practice), you move on to a longer three-hour glucose tolerance test. During that second test, your blood is drawn at fasting and then at one, two, and three hours after drinking a higher-concentration glucose solution. Elevated readings at two or more of those time points confirm gestational diabetes.
The cutoffs for that three-hour test vary slightly depending on which diagnostic criteria your provider uses, which is why you might see different numbers from different sources. What’s consistent is that gestational diabetes requires closer monitoring, because sustained high blood sugar during pregnancy affects both the parent and the baby.
Ranges for Children With Diabetes
Children and adolescents with type 1 diabetes use slightly different targets than adults. Before meals, the recommended range is 70 to 144 mg/dL. After meals, the goal widens to 70 to 180 mg/dL. At bedtime, the target drops back to 70 to 144 mg/dL to reduce the risk of overnight lows.
For kids using continuous glucose monitors, the goal is to spend more than 70% of the day (roughly 17 out of 24 hours) with readings between 70 and 180 mg/dL. Less than 4% of the day should be spent below 70 mg/dL, and less than 1% below 54 mg/dL, since drops that low can cause confusion, seizures, or loss of consciousness. On the high end, less than 25% of the day should be above 180 mg/dL and less than 5% above 250 mg/dL.
Continuous Glucose Monitor Targets
If you wear a continuous glucose monitor, blood sugar ranges take on a different dimension. Instead of isolated finger-stick readings, you’re looking at trends throughout the day. The key metric is called “time in range,” which is the percentage of the day your glucose stays between 70 and 180 mg/dL.
The American Diabetes Association recommends aiming for at least 70% time in range. That translates to about 17 hours a day with your blood sugar between those two numbers. The remaining time will naturally split between brief highs after meals and occasional dips. What matters most is minimizing the extremes, particularly time spent below 70 mg/dL, where you’d feel shaky, sweaty, or lightheaded, and time above 250 mg/dL, where sustained highs start doing damage to blood vessels and nerves.
Some providers also track “time in tight range,” which narrows the window to 70 to 144 mg/dL. Spending more than 50% of the day in that tighter band correlates with A1C levels at or below 6.5%, which is increasingly the goal for people who have access to advanced diabetes technology.
When Blood Sugar Becomes Dangerous
On the low end, blood sugar below 70 mg/dL is considered hypoglycemia. You’ll usually feel it: shakiness, sweating, a racing heart, irritability, or sudden hunger. Below 54 mg/dL is classified as clinically significant hypoglycemia and can impair your ability to think clearly or treat yourself. This is most relevant for people taking insulin or certain oral medications that lower blood sugar.
On the high end, readings above 250 mg/dL are a signal to check for ketones, which are acids your body produces when it starts burning fat instead of glucose for energy. If your blood sugar stays at 300 mg/dL or above, that’s an emergency. At those levels, you’re at risk for diabetic ketoacidosis, a condition where ketone levels become dangerously high, making your blood acidic. Symptoms include nausea, vomiting, abdominal pain, fruity-smelling breath, and rapid breathing. Diabetic ketoacidosis develops most often in people with type 1 diabetes but can occur in type 2 as well, particularly during illness or infection.
Why These Numbers Aren’t One-Size-Fits-All
The ranges above are population-level guidelines. Your personal targets may differ. Older adults, for instance, are sometimes given slightly higher targets because the risk of a dangerous low outweighs the long-term benefit of tight control. People with a recent diabetes diagnosis and no complications might aim for tighter numbers. Pregnancy, kidney disease, and the type of medication you take all shift the goalposts.
What stays constant is the pattern: fasting below 100 mg/dL, post-meal below 140 mg/dL, and A1C below 5.7% represent healthy glucose metabolism. Anything consistently above those numbers means your body is struggling to manage glucose on its own, and the degree to which it’s struggling determines whether you’re looking at prediabetes or diabetes.