A normal fasting blood sugar is below 100 mg/dL (5.6 mmol/L). That’s the number most people are looking for, and it applies to adults who haven’t eaten for at least eight hours. But “normal” shifts depending on when you last ate, your age, and whether you’re pregnant, so the full picture is worth understanding.
Normal Fasting Blood Sugar
When doctors talk about blood sugar, they usually mean fasting blood sugar, measured after you’ve gone without food for at least eight hours (typically first thing in the morning). For a healthy adult, that number should land below 100 mg/dL. Once it hits 100 to 125 mg/dL, it falls into the prediabetes range, sometimes called impaired fasting glucose. A reading of 126 mg/dL or higher on two separate tests indicates diabetes.
These cutoffs aren’t arbitrary. They reflect the point at which the risk of long-term complications, particularly damage to blood vessels, the kidneys, and the eyes, starts to climb meaningfully.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal as your body breaks down carbohydrates into glucose. In a healthy person, it peaks about 60 to 90 minutes after eating and then drops back toward baseline within two hours. A two-hour reading below 140 mg/dL is considered normal. Between 140 and 199 mg/dL at the two-hour mark signals prediabetes (also called impaired glucose tolerance), and 200 mg/dL or above points to diabetes.
The speed of that post-meal rise depends heavily on what you ate. A bowl of white rice will spike blood sugar faster and higher than a plate of grilled chicken and vegetables. Fiber, fat, and protein all slow digestion and blunt the glucose peak, which is one reason balanced meals matter for blood sugar control even in people without diabetes.
How Your Body Keeps Blood Sugar Stable
Your pancreas runs the show. It produces two hormones that work as a counterbalancing pair: insulin and glucagon. When blood sugar rises after eating, the pancreas releases insulin, which moves glucose out of the blood and into cells where it’s used for energy. When blood sugar drops too low, say between meals or overnight, the pancreas releases glucagon instead. Glucagon signals the liver to convert stored glucose back into a usable form and release it into the bloodstream. It also triggers the body to produce glucose from other sources, like amino acids from protein.
When this system works well, blood sugar stays within a surprisingly tight window throughout the day and night. Problems develop when the pancreas can’t produce enough insulin (as in type 1 diabetes), or when the body’s cells stop responding to insulin efficiently (as in type 2 diabetes and prediabetes).
The A1C Test and What It Tells You
A single blood sugar reading is a snapshot. The A1C test gives you the bigger picture. It measures the percentage of hemoglobin in your red blood cells that has glucose attached to it, reflecting your average blood sugar over roughly the past two to three months. A normal A1C is below 5.7%. Between 5.7% and 6.4% falls in the prediabetes range. An A1C of 6.5% or higher indicates diabetes.
Because it captures a longer timeframe, the A1C is less affected by a single bad meal or a stressful morning. It’s also a useful tracking tool: if your A1C is trending upward over annual checkups, that’s a signal worth paying attention to even if individual glucose readings still look fine.
Normal Ranges for Children
Children’s blood sugar targets are slightly wider than adults’, partly because young kids eat unpredictably and partly because severe low blood sugar is especially risky for developing brains. General pediatric targets break down by age:
- Under 5 years: 80 to 200 mg/dL
- 5 to 11 years: 70 to 180 mg/dL
- 12 and older: 70 to 150 mg/dL
These ranges apply throughout the day, including after meals. As children get older, their target window narrows and starts to approach adult levels.
Blood Sugar Targets During Pregnancy
Pregnancy tightens the acceptable range considerably. High blood sugar during pregnancy can affect fetal development, so the targets are stricter than usual. The American Diabetes Association recommends these goals for pregnant women with gestational diabetes:
- Fasting: below 95 mg/dL
- One hour after eating: below 140 mg/dL
- Two hours after eating: below 120 mg/dL
These same targets generally apply to pregnant women with pre-existing type 1 or type 2 diabetes, though the lower end of fasting glucose should stay above 70 mg/dL to avoid dangerous drops. Gestational diabetes typically resolves after delivery, but it does increase the risk of developing type 2 diabetes later in life.
Targets for Older Adults
For adults over 65, blood sugar targets are often intentionally relaxed. The risk equation shifts with age: dangerously low blood sugar (hypoglycemia) becomes more harmful, potentially causing falls, confusion, and cardiac events. Meanwhile, the long-term complications of slightly elevated blood sugar matter less when life expectancy is shorter.
For healthy older adults, an A1C below 7.5% is a reasonable goal, with fasting glucose between 140 and 150 mg/dL. For those managing serious health conditions or cognitive decline, targets may loosen further to an A1C below 8% or even 8.5%, with the priority being to avoid both dangerously low and extremely high readings (above 350 mg/dL). These are individual decisions that depend on overall health and quality of life rather than a one-size-fits-all number.
When Blood Sugar Drops Too Low
For people without diabetes, blood sugar below 55 mg/dL is considered clinical hypoglycemia. Symptoms usually start before you reach that threshold: shakiness, sweating, irritability, a racing heartbeat, and sudden hunger are common early signs. More severe drops can cause confusion, blurred vision, and loss of consciousness.
Hypoglycemia in non-diabetic adults is uncommon. When it does happen, the causes typically involve prolonged fasting, heavy alcohol consumption, or rarely a hormone-producing tumor. In people with diabetes, it’s much more common and usually related to medication timing or missed meals.
Getting Accurate Readings at Home
If you’re testing blood sugar with a home glucose meter, a few common factors can throw off your results. Expired or improperly stored test strips are one of the biggest culprits. Strips should stay in their sealed container, away from heat and humidity.
Wash your hands with soap and water before testing. Residue from food, lotion, or even hand sanitizer can contaminate the sample. If you use an alcohol wipe, let the skin dry completely before pricking. Dehydration and anemia (low red blood cell count) can also make readings less reliable. And if you test from a site other than your fingertip, such as your forearm, the reading may lag behind your actual blood sugar during times when levels are changing quickly. Fingertip samples are the most accurate in those moments.
Apply a generous drop of blood to the strip in one touch. Adding a second drop after the first won’t correct a small sample; it will usually just produce an error or an inaccurate result.