A normal fasting blood sugar level is below 100 mg/dL. If you’re checking after a meal, it should stay under 140 mg/dL in a healthy adult. These numbers shift depending on whether you’re fasting, pregnant, managing diabetes, or checking a child’s levels, so the full picture is worth understanding.
Fasting Blood Sugar Ranges
Fasting blood sugar is measured after at least eight hours without eating, typically first thing in the morning. The thresholds are straightforward:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher on two separate tests
That gap between 100 and 125 is important. Prediabetes means your body is already struggling to manage glucose efficiently, but the process is often reversible with changes to diet, exercise, and weight. A single reading in this range doesn’t mean much on its own, since stress, poor sleep, and illness can temporarily push numbers up. Two or more elevated readings paint a clearer picture.
After-Meal Targets
Blood sugar naturally rises after you eat. In a person without diabetes, it typically peaks about 60 to 90 minutes after a meal and settles back down within two hours. The general target is to stay below 180 mg/dL two hours after the start of a meal. Most healthy adults will actually land well below that, often under 140 mg/dL, but the 180 threshold is the clinical benchmark used for people managing diabetes.
What you ate matters. A meal heavy in refined carbohydrates (white bread, sugary drinks, pasta) will spike your blood sugar faster and higher than one built around protein, fiber, and healthy fats. If you’re consistently seeing post-meal readings above 140, that’s worth discussing with your doctor even if your fasting numbers look fine. Some people have normal fasting glucose but elevated post-meal spikes, a pattern that can go undetected without targeted testing.
A1C: The Bigger Picture
A1C measures your average blood sugar over the past two to three months. It reflects how much glucose has been attaching to your red blood cells over their lifespan, giving a broader view than any single finger stick.
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
A1C is useful because it isn’t thrown off by what you ate last night or how stressed you felt this morning. It’s the number doctors rely on most for diagnosis and for tracking how well diabetes management is working over time. For most adults with diabetes, the treatment goal is to keep A1C below 7%, though individual targets vary.
Targets During Pregnancy
Pregnancy tightens the acceptable range significantly because elevated blood sugar affects fetal development. For gestational diabetes, the targets are:
- Fasting: 95 mg/dL or below
- One hour after a meal: 140 mg/dL or below
- Two hours after a meal: 120 mg/dL or below
Women who had type 1 or type 2 diabetes before becoming pregnant have even stricter goals: fasting levels between 60 and 99 mg/dL, post-meal peaks between 100 and 129 mg/dL, and an A1C below 6.0%. These tighter windows reduce the risk of complications like preeclampsia, large birth weight, and neonatal blood sugar problems.
Targets for Children
Children managing type 1 diabetes have wider acceptable ranges than adults, partly because their daily activity levels fluctuate more and partly because low blood sugar is especially risky in young kids. General pediatric targets:
- 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
The wider range for younger children reflects the priority of avoiding dangerously low blood sugar, since toddlers and preschoolers can’t always recognize or communicate symptoms of a low.
When Blood Sugar Drops Too Low
Blood sugar below 70 mg/dL is considered low (hypoglycemia). This is most common in people taking insulin or certain diabetes medications, but it can happen to anyone after prolonged fasting, intense exercise, or excessive alcohol intake.
At 70 mg/dL, you might feel shaky, sweaty, irritable, or suddenly hungry. These are your body’s early warning signals. Below 54 mg/dL, the situation becomes more serious. Confusion, blurred vision, difficulty speaking, and loss of coordination can set in. At the most severe level, a person may need someone else’s help to treat the episode because they can’t safely manage it themselves.
If you experience symptoms of low blood sugar, the standard response is to consume 15 grams of fast-acting carbohydrate (four glucose tablets, half a cup of juice, or a tablespoon of honey), wait 15 minutes, and recheck. Repeat if you’re still below 70.
When Blood Sugar Climbs Dangerously High
Readings above 240 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. Small amounts of ketones are harmless, but high levels can lead to diabetic ketoacidosis, a life-threatening condition that requires emergency treatment. Symptoms include nausea, vomiting, abdominal pain, fruity-smelling breath, and rapid breathing.
Persistently elevated readings above 180 mg/dL, even without ketones, cause gradual damage to blood vessels, nerves, kidneys, and eyes over months and years. This is why long-term averages (A1C) matter as much as individual readings.
Time in Range for Continuous Monitors
If you wear a continuous glucose monitor (CGM), the key metric is “time in range,” which tracks 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:
- In range (70 to 180 mg/dL): more than 70% of the day, roughly 17 hours
- Below 70 mg/dL: less than 4% of the day, under 1 hour
- Above 180 mg/dL: less than 25% of the day, under 6 hours
- Above 250 mg/dL: less than 5% of the day, under about 1 hour
For older adults or people at higher risk of complications from low blood sugar, the goals are more relaxed. Time in range drops to a minimum of 50% (12 hours), and time spent below 70 mg/dL is capped at less than 1%, or about 15 minutes per day. The priority shifts toward avoiding dangerous lows rather than keeping glucose tightly controlled.
Getting an Accurate Reading
A few common factors can throw off a finger-stick reading. Wash your hands before testing. Residue from food, lotion, or even hand sanitizer can artificially raise results. If you use an alcohol wipe, let the site dry completely before pricking. Dehydration and anemia can also reduce accuracy.
Test strips are sensitive to moisture and heat, so store them in their sealed container and toss any that are expired or damaged. If you test from an alternate site like your forearm, keep in mind that those readings lag behind fingertip samples when blood sugar is changing quickly, such as right after a meal or during exercise. When in doubt, retest from a fingertip.