For most healthy adults, a normal fasting blood sugar is below 100 mg/dL, and levels after eating typically stay under 140 mg/dL. Children have slightly wider acceptable ranges, and targets shift again during pregnancy and in older age. Here’s how those numbers break down across life stages and testing methods.
How Blood Sugar Is Measured
Blood sugar numbers come from a few different tests, and each one has its own “normal” threshold. The most common is the fasting blood glucose test, taken after at least 8 hours without food. There’s also the oral glucose tolerance test, which measures your blood sugar two hours after drinking a sugary solution. And then there’s the A1C test, which reflects your average blood sugar over the past two to three months as a percentage.
Throughout a normal day, blood sugar in a healthy person fluctuates between roughly 82 mg/dL and 110 mg/dL, rising to around 140 mg/dL after a full meal before settling back down. Those swings are completely normal. The diagnostic thresholds below represent the cutoffs where risk begins to change.
Normal Ranges for Adults
The American Diabetes Association defines three categories based on fasting blood glucose:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
On the oral glucose tolerance test (the two-hour post-drink measurement), the cutoffs are:
- Normal: below 140 mg/dL
- Prediabetes: 140 to 199 mg/dL
- Diabetes: 200 mg/dL or higher
For A1C, which is expressed as a percentage rather than mg/dL:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
These thresholds apply broadly to adults, and they don’t change between your 20s and your 50s. A fasting level of 95 mg/dL is considered normal whether you’re 25 or 55. Where age starts to matter is at the extremes: childhood and older adulthood.
Normal Ranges for Children
Children’s blood sugar targets are wider than adult ranges, especially for younger kids. Their bodies are still developing, and they’re more vulnerable to the effects of low blood sugar, so the acceptable floor and ceiling are both adjusted. Dartmouth Health Children’s provides these goal ranges:
- 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
Notice how the range narrows as children get older. A toddler’s blood sugar can safely swing higher than a teenager’s. By age 12, the target range begins to approach adult levels, and by late adolescence, the standard adult thresholds generally apply. These pediatric ranges are particularly relevant for children with diabetes who are actively monitoring their glucose, but they also reflect what’s physiologically normal at each stage of development.
Blood Sugar Targets During Pregnancy
Pregnancy tightens the window for what counts as normal. Elevated blood sugar during pregnancy, called gestational diabetes, can affect both the mother and the baby, so the recommended targets are stricter than standard adult ranges. The American College of Obstetricians and Gynecologists recommends:
- Before a meal: 95 mg/dL or less
- One hour after a meal: 140 mg/dL or less
- Two hours after a meal: 120 mg/dL or less
That fasting target of 95 mg/dL is lower than the general adult cutoff of 100 mg/dL. It may seem like a small difference, but during pregnancy even modestly elevated glucose levels can increase the risk of complications like high birth weight, early delivery, and preeclampsia. Most pregnant women are screened for gestational diabetes between weeks 24 and 28 using a glucose tolerance test.
How Targets Shift for Older Adults
For adults over 65, blood sugar targets often become less strict rather than more strict. This might seem counterintuitive, but there’s a practical reason: the risks of low blood sugar become more dangerous with age. A blood sugar drop below 70 mg/dL can cause dizziness, confusion, and falls, all of which carry serious consequences for older adults.
The American Diabetes Association notes that A1C goals vary based on age, other medical conditions, and a person’s ability to recognize when their blood sugar is dropping. For most adults with diabetes, the general A1C target is below 7%. But for older adults with multiple health conditions or limited life expectancy, a target of 7.5% to 8% is often more appropriate. The priority shifts from tight glucose control toward avoiding dangerous lows.
For older adults without diabetes, the same standard thresholds apply: fasting glucose below 100 mg/dL and A1C below 5.7%. Age alone doesn’t change what “normal” means. It changes how aggressively blood sugar is managed when it’s already elevated.
What Counts as Low Blood Sugar
The focus is usually on numbers that are too high, but blood sugar can also drop too low. The CDC defines low blood sugar (hypoglycemia) as anything below 70 mg/dL. Severe low blood sugar is below 54 mg/dL, which can cause seizures, loss of consciousness, or the inability to treat yourself without help.
Symptoms of mild low blood sugar include shakiness, sweating, irritability, and sudden hunger. These episodes are most common in people taking insulin or certain diabetes medications, but they can also happen in people without diabetes after prolonged fasting, intense exercise, or excessive alcohol intake. If your blood sugar regularly dips below 70 mg/dL, that pattern is worth investigating regardless of your age.
Finger-Stick vs. Lab Test Accuracy
If you’re testing at home with a finger-stick glucometer, your readings may differ slightly from what a lab blood draw would show. Research comparing the two methods finds that finger-stick readings tend to run about 5 to 6 mg/dL different from venous lab results. That gap is statistically measurable but not clinically significant for most purposes.
The bigger issue is consistency. Finger-stick monitors have a moderate correlation with lab values, meaning individual readings can occasionally be off by more than the average. Factors like unwashed hands (residual sugar from food), temperature extremes, dehydration, and test strip quality can all affect accuracy. For diagnostic purposes, like confirming prediabetes or diabetes, a lab draw is the standard. Home monitors are best used for tracking trends over time rather than treating any single reading as definitive.
What These Numbers Mean in Practice
A single blood sugar reading is a snapshot, not a diagnosis. Your glucose levels shift throughout the day depending on what you’ve eaten, how active you’ve been, your stress level, and how well you slept. A healthy person’s blood sugar might sit at 85 mg/dL before breakfast, spike to 135 mg/dL after a carb-heavy meal, and return to the 90s within a couple of hours. All of that is normal.
The numbers that matter most are the ones that form patterns. A fasting glucose of 105 mg/dL on one test could be a fluke. Repeated fasting readings in the 100 to 125 range put you in prediabetes territory, which affects roughly 1 in 3 American adults. At that stage, blood sugar is elevated enough to cause gradual damage but not yet high enough for a diabetes diagnosis. The good news is that prediabetes is the stage where lifestyle changes, particularly weight loss, increased physical activity, and reduced refined carbohydrate intake, are most effective at reversing the trend.
If you’re checking your levels at home, testing first thing in the morning before eating gives you the most comparable reading to the clinical fasting glucose standards listed above. Post-meal readings are most informative when taken about two hours after your first bite, which is when blood sugar should be settling back toward baseline in a healthy body.