A healthy fasting blood sugar level falls between 70 and 99 mg/dL for adults without diabetes. That single range, though, only tells part of the story. Blood sugar targets shift depending on when you last ate, whether you have diabetes or prediabetes, your age, and whether you’re pregnant. Here’s a complete breakdown of what the numbers mean.
Normal Fasting Blood Sugar
Fasting blood sugar is measured after at least eight hours without food, typically first thing in the morning. For a healthy adult without diabetes, the target is 70 to 99 mg/dL (3.9 to 5.5 mmol/L). Some people naturally run a bit lower, and values between 50 and 70 mg/dL can be perfectly normal if you feel fine and have no history of diabetes.
Once fasting levels reach 100 mg/dL, they enter a gray zone. The American Diabetes Association defines the ranges this way:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher (confirmed on two separate tests)
Prediabetes means your body is starting to struggle with processing sugar, but the condition is reversible with lifestyle changes. About 1 in 3 American adults falls into this range without knowing it.
Blood Sugar After Eating
Your blood sugar rises after every meal, peaks around 60 to 90 minutes later, and then gradually returns to baseline. For someone without diabetes, the two-hour mark after eating should show a reading below 140 mg/dL. If you have diabetes, the goal is typically below 180 mg/dL two hours after a meal.
This post-meal number matters because it reveals how effectively your body clears sugar from the bloodstream. You can have a normal fasting level yet still spike too high after meals, which is one reason doctors sometimes order a glucose tolerance test rather than relying on fasting numbers alone.
The A1C Test and Long-Term Averages
While a fingerstick or fasting blood draw captures a single moment, the A1C test reflects your average blood sugar over the previous two to three months. It works by measuring the percentage of hemoglobin (a protein in red blood cells) that has bonded with sugar. The diagnostic thresholds are:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
A1C is convenient because it doesn’t require fasting, but it isn’t perfect for everyone. Individual differences in red blood cell lifespan can cause the test to read higher or lower than your actual average sugar level. Conditions that affect red blood cells, such as anemia or certain hemoglobin variants, can also skew results. When there’s a mismatch between A1C and daily glucose readings, doctors may rely more heavily on direct blood sugar measurements.
The Glucose Tolerance Test
During an oral glucose tolerance test, you drink a sugary solution and have your blood drawn two hours later. This test is especially common during pregnancy screening but is also used to diagnose prediabetes and diabetes in the general population. The two-hour cutoffs are:
- Normal: below 140 mg/dL
- Prediabetes: 140 to 199 mg/dL
- Diabetes: 200 mg/dL or higher
Blood Sugar Targets During Pregnancy
Pregnancy requires tighter blood sugar control because even moderately elevated glucose can affect fetal development. The American Diabetes Association recommends these targets for women with gestational diabetes or pre-existing diabetes during pregnancy:
- Fasting: below 95 mg/dL
- One hour after eating: below 140 mg/dL
- Two hours after eating: below 120 mg/dL
For women with type 1 or type 2 diabetes, the fasting target range is 70 to 95 mg/dL, with the same post-meal ceilings. These goals may be loosened if hitting them causes frequent low blood sugar episodes, since hypoglycemia during pregnancy carries its own risks.
Targets for Children With Diabetes
Children with type 1 diabetes have slightly different targets than adults because the risks of low blood sugar are harder to manage in younger kids who may not recognize or communicate symptoms. At the University of Iowa Stead Family Children’s Hospital, the recommended ranges are:
For children ages 6 and older: 70 to 150 mg/dL before meals, 90 to 150 mg/dL at bedtime and overnight. For children ages 1 to 5: 80 to 150 mg/dL before meals, 90 to 150 mg/dL at bedtime and overnight. The A1C goal for children under 18 is generally below 7%, though less stringent targets (below 7.5% to 8%) are sometimes appropriate for very young children or those with hypoglycemia unawareness.
When Blood Sugar Drops Too Low
Low blood sugar, or hypoglycemia, is classified in three levels of severity:
- Level 1: 54 to 69 mg/dL. You may feel shaky, sweaty, or hungry. This usually resolves with a fast-acting carbohydrate like juice or glucose tablets.
- Level 2: below 54 mg/dL. This is clinically significant and requires prompt treatment. Confusion, blurred vision, and difficulty concentrating are common.
- Level 3: any reading where you need someone else’s help to recover, regardless of the number. This can involve seizures or loss of consciousness.
Hypoglycemia is most common in people taking insulin or certain oral diabetes medications. It’s rare in people without diabetes, though it can happen after prolonged fasting, intense exercise, or excessive alcohol intake.
When Blood Sugar Gets Dangerously High
On the opposite end, a blood sugar level above 200 mg/dL with symptoms like excessive thirst, frequent urination, and fatigue typically signals uncontrolled diabetes. Two specific emergencies can develop at very high levels.
Diabetic ketoacidosis (DKA) occurs when the body, unable to use sugar for fuel, breaks down fat at a dangerous rate, producing acids called ketones. It’s most common in type 1 diabetes and historically defined by glucose above 250 mg/dL, though recent consensus has lowered the threshold to 200 mg/dL. Importantly, DKA can even occur with near-normal glucose levels in some cases, a condition called euglycemic DKA. The diagnosis requires elevated ketones and metabolic acidosis in addition to high sugar.
Hyperglycemic hyperosmolar state (HHS) tends to occur in type 2 diabetes, often with blood sugar exceeding 600 mg/dL. It develops more slowly than DKA, over days or weeks, and involves severe dehydration and confusion without the significant ketone buildup seen in DKA. Both conditions are medical emergencies.
Time in Range for CGM Users
If you wear a continuous glucose monitor (CGM), your doctor may talk about “time in range” rather than individual readings. This metric measures what percentage of the day your blood sugar stays between 70 and 180 mg/dL. The international consensus targets for most adults with type 1 or type 2 diabetes are:
- Time in range (70 to 180 mg/dL): more than 70% of the day, roughly 17 hours
- Time below 70 mg/dL: less than 4% of the day, under 1 hour
- Time below 54 mg/dL: less than 1% of the day, under 15 minutes
- Time above 180 mg/dL: less than 25% of the day, under 6 hours
- Time above 250 mg/dL: less than 5% of the day, under 1 hour and 12 minutes
Time in range gives a fuller picture than A1C alone because two people with the same A1C can have very different daily patterns. One might stay steadily in range while the other swings between highs and lows that average out to the same number. The CGM data reveals those swings, making it easier to fine-tune management.