A regular (normal) blood sugar level is below 100 mg/dL when measured after fasting, and below 140 mg/dL when measured two hours after eating. These are the thresholds used to separate healthy blood sugar from the ranges that signal prediabetes or diabetes. Where you fall relative to these numbers depends on when you last ate, your age, and whether you’re pregnant.
Normal Fasting Blood Sugar
Fasting blood sugar is the most common way to check glucose levels, and it’s measured after you haven’t eaten for at least eight hours (typically first thing in the morning). A fasting level below 100 mg/dL (5.6 mmol/L) is considered normal for adults. If your result lands between 100 and 125 mg/dL, that falls into the prediabetes range. A reading of 126 mg/dL or higher on two separate tests meets the diagnostic threshold for diabetes.
Most healthy adults with no blood sugar issues will see fasting numbers somewhere between 74 and 100 mg/dL. It’s normal for your number to shift slightly from day to day based on sleep, stress, and what you ate the night before. A single reading slightly above 100 doesn’t mean you have prediabetes, which is why doctors typically confirm with a repeat test.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal as your body breaks down carbohydrates into glucose. In a healthy person, insulin brings those levels back down within a couple of hours. A normal reading two hours after eating is below 140 mg/dL. If that number falls between 140 and 199 mg/dL, it suggests prediabetes. A result of 200 mg/dL or higher indicates diabetes.
This post-meal measurement is formally called an oral glucose tolerance test, and it involves drinking a standardized sugary solution at a lab rather than just eating a regular meal. Your doctor might order this test if your fasting number is borderline or if they suspect your body has trouble processing sugar even though your fasting level looks fine.
The A1C Test: Your 3-Month Average
While fasting and post-meal tests capture a single moment, the A1C test reflects your average blood sugar over the past two to three months. It measures the percentage of your red blood cells that have glucose attached to them. A normal A1C is below 5.7%. An A1C between 5.7% and 6.4% indicates prediabetes, and 6.5% or higher means diabetes.
The A1C is useful because it isn’t thrown off by what you ate yesterday or how well you slept. It gives a broader picture of how your body manages sugar over time. Many doctors use it alongside a fasting glucose test to get the most complete assessment.
When Blood Sugar Drops Too Low
Normal blood sugar has a floor, not just a ceiling. A reading below 70 mg/dL is considered low blood sugar (hypoglycemia), and it can cause shakiness, sweating, confusion, dizziness, and irritability. Below 54 mg/dL is classified as severely low and can become dangerous, potentially leading to seizures or loss of consciousness if not treated quickly.
Low blood sugar is most common in people taking insulin or certain diabetes medications, but it can also happen in people without diabetes after prolonged fasting, intense exercise, or heavy alcohol consumption. If you notice symptoms, eating or drinking something with fast-acting sugar (juice, glucose tablets, regular soda) typically brings levels back up within 15 minutes.
Normal Ranges During Pregnancy
Pregnant women are held to tighter blood sugar targets because elevated glucose can affect fetal development. The recommended ranges during pregnancy are a fasting glucose of 70 to 95 mg/dL, under 140 mg/dL one hour after eating, and under 120 mg/dL two hours after eating. These targets apply whether you had diabetes before pregnancy or developed gestational diabetes during it.
Most pregnant women are screened for gestational diabetes between weeks 24 and 28 with a glucose tolerance test. The stricter numbers reflect the fact that even mildly elevated blood sugar during pregnancy can increase the risk of complications like high birth weight and preterm delivery.
How Children’s Levels Differ
Children’s normal blood sugar ranges are slightly different from adults’. Kids under two typically have a normal fasting range of 60 to 100 mg/dL, while adults fall in the 74 to 106 mg/dL range. Newborns run even lower, with normal levels between 30 and 60 mg/dL in the first days of life. These numbers gradually rise as children grow, eventually aligning with adult ranges by adolescence.
mg/dL vs. mmol/L
If you live in the United States, your blood sugar results come in mg/dL. Most other countries use mmol/L. To convert between the two, divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL. So a normal fasting level of 100 mg/dL equals about 5.6 mmol/L, and the diabetes threshold of 126 mg/dL equals 7.0 mmol/L.
Quick Reference: Blood Sugar Ranges
- Normal fasting: below 100 mg/dL (5.6 mmol/L)
- Prediabetes fasting: 100 to 125 mg/dL
- Diabetes fasting: 126 mg/dL or higher
- Normal 2 hours after eating: below 140 mg/dL
- Normal A1C: below 5.7%
- Low blood sugar: below 70 mg/dL
- Severely low: below 54 mg/dL