A good fasting blood sugar level for a healthy adult is between 70 and 99 mg/dL. After eating, blood sugar naturally rises, but it should come back below 140 mg/dL within two hours. These numbers shift depending on whether you’re managing diabetes, pregnant, or simply trying to understand a lab result, so the full picture is worth knowing.
Normal Fasting Blood Sugar
When you haven’t eaten for at least eight hours, a reading between 70 and 99 mg/dL (3.9 to 5.5 mmol/L) is considered healthy. Some people naturally sit lower, in the 50 to 70 mg/dL range, without any symptoms or problems. The key is consistency: your fasting number should land in roughly the same zone most mornings.
A fasting reading between 100 and 125 mg/dL falls into the prediabetes range. At 126 mg/dL or above on two separate tests, the result meets the diagnostic threshold for diabetes. These cutoffs matter because prediabetes often produces no symptoms at all, which is why routine bloodwork catches it before anything feels wrong.
Blood Sugar After Meals
Your blood sugar peaks about 60 to 90 minutes after you start eating, then gradually drops. In a person without diabetes, it should fall below 140 mg/dL by the two-hour mark. Most healthy adults actually return to their baseline well before that.
The size, speed, and composition of a meal all influence the spike. A plate of white rice will push your blood sugar higher and faster than the same number of calories from lentils and vegetables, because refined carbohydrates break down quickly. Pairing carbs with protein, fat, or fiber slows digestion and flattens the curve.
Targets if You Have Diabetes
The goals are slightly wider for people managing diabetes. The CDC lists these typical targets for adults with type 1 or type 2 diabetes:
- Before a meal: 80 to 130 mg/dL
- Two hours after starting a meal: less than 180 mg/dL
These ranges acknowledge that blood sugar is harder to control when the body either doesn’t produce enough insulin or doesn’t respond to it efficiently. Staying consistently within these windows reduces the long-term risk of complications affecting the eyes, kidneys, nerves, and heart. Your care team may tighten or loosen these targets based on your age, how long you’ve had diabetes, and whether you experience frequent lows.
What Your A1C Tells You
While a finger stick or lab draw captures a single moment, the A1C test reflects your average blood sugar over roughly two to three months. It measures the percentage of hemoglobin (a protein in red blood cells) that has sugar attached to it. The higher your blood sugar has been running, the higher that percentage climbs.
The American Diabetes Association breaks it down like this:
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
An A1C of 5.7% translates to an average blood sugar of roughly 117 mg/dL. At 6.5%, the average sits around 140 mg/dL. Because it smooths out daily highs and lows, A1C gives a more reliable picture of overall control than any single reading can.
Time in Range for CGM Users
If you wear a continuous glucose monitor, the metric to watch is “time in range,” meaning the percentage of the day your blood sugar stays between 70 and 180 mg/dL. The American Diabetes Association recommends spending at least 70% of readings in that window, which works out to roughly 17 out of every 24 hours.
Time in range captures something A1C misses: variability. Two people can have the same A1C, but one might swing wildly between 50 and 250 mg/dL while the other hovers steadily between 90 and 150. The steadier pattern is healthier, and time in range rewards that stability.
Blood Sugar Targets During Pregnancy
Pregnancy tightens the acceptable range because elevated blood sugar can affect fetal development. The American College of Obstetricians and Gynecologists recommends these goals for pregnant women with diabetes or gestational diabetes:
- Fasting: below 95 mg/dL
- One hour after eating: below 140 mg/dL
- Two hours after eating: below 120 mg/dL
These targets are stricter than the general diabetes guidelines, which is why pregnant women often check their blood sugar four or more times a day. The two-hour post-meal cutoff of 120 mg/dL, in particular, is notably lower than the 180 mg/dL target used outside of pregnancy.
When Blood Sugar Drops Too Low
Low blood sugar, or hypoglycemia, generally starts at readings below 70 mg/dL. It’s most common in people who take insulin or certain oral diabetes medications, but it can happen to anyone after prolonged fasting or intense exercise. Symptoms include shakiness, sweating, a racing heartbeat, irritability, and difficulty concentrating. At very low levels, confusion and loss of consciousness become risks.
If you feel symptoms of a low, checking your blood sugar and eating 15 to 20 grams of fast-acting carbohydrate (a few glucose tablets, half a cup of juice, or a tablespoon of honey) is the standard approach. Wait 15 minutes, recheck, and repeat if you’re still below 70.
Surprising Things That Raise Blood Sugar
Food gets all the attention, but plenty of non-food factors push blood sugar up. Even one night of poor sleep makes your body use insulin less effectively the next day. Dehydration concentrates the sugar already in your bloodstream, so a reading can look worse simply because you haven’t had enough water. Stress, whether emotional or physical (including sunburn), triggers hormones that tell the liver to release stored glucose.
Caffeine affects some people more than others, raising blood sugar even in black coffee with no sweetener. Skipping breakfast has been linked to higher post-meal spikes at both lunch and dinner. Blood sugar also tends to be harder to control later in the day, and many people experience a natural early-morning rise called the “dawn phenomenon,” driven by a surge of hormones that happens whether or not you have diabetes.
Some less obvious culprits: certain nasal decongestant sprays can trigger the liver to release glucose, and chronic gum disease creates low-grade inflammation that interferes with blood sugar regulation. Knowing these factors exist helps explain why a reading might be higher than expected even when your meals haven’t changed.