A normal fasting blood sugar is below 100 mg/dL, and a normal reading two hours after eating is below 140 mg/dL. Those two numbers are the baseline, but the full picture includes thresholds for prediabetes, diabetes, low blood sugar, and special targets for pregnancy and older adults.
Normal Blood Sugar Levels
For a healthy adult without diabetes, blood sugar stays within a relatively tight window throughout the day. Before eating (fasting), a normal level is under 100 mg/dL (5.6 mmol/L). Two hours after a meal, it should be under 140 mg/dL (7.8 mmol/L). Your body manages this automatically: the pancreas releases insulin after you eat, which moves sugar from your blood into your cells for energy, then production tapers off as levels drop back down.
If you use a continuous glucose monitor or see readings in mmol/L (common outside the United States), you can convert between the two units by dividing mg/dL by 18. So 100 mg/dL equals about 5.6 mmol/L, and 140 mg/dL equals about 7.8 mmol/L.
Prediabetes and Diabetes Thresholds
The American Diabetes Association uses three distinct zones for fasting blood sugar:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
These same categories apply to A1C, a blood test that reflects your average blood sugar over roughly three months. A normal A1C is below 5.7%. Prediabetes falls between 5.7% and 6.4%. An A1C of 6.5% or higher indicates diabetes. A diabetes diagnosis typically requires two separate tests confirming elevated levels, not just a single reading.
Prediabetes is worth paying attention to because it signals your body is losing its ability to regulate sugar efficiently, but the process is often reversible with changes to diet, exercise, and weight.
Low Blood Sugar Levels
Blood sugar that drops too low (hypoglycemia) is classified in stages. Level 1 hypoglycemia is a reading between 54 and 69 mg/dL. You might feel shaky, sweaty, or lightheaded, and eating a fast-acting carbohydrate like juice or glucose tablets usually resolves it quickly. Level 2 is below 54 mg/dL, which is more serious and can cause confusion, blurred vision, or difficulty speaking. Level 3 is any episode severe enough that you need someone else’s help to recover, regardless of the exact number on the meter.
Hypoglycemia is most common in people taking insulin or certain diabetes medications, but it can occasionally happen in people without diabetes after prolonged fasting, heavy exercise, or excessive alcohol intake.
Targets for People With Diabetes
If you have Type 1 or Type 2 diabetes, the goal isn’t to maintain the same narrow range as someone without diabetes. Instead, targets are set to balance good control against the risk of dangerous lows. The general target for most adults with diabetes is spending at least 70% of the day between 70 and 180 mg/dL. For people at higher risk of hypoglycemia, that target drops to at least 50% of the day in range.
Before meals, most people with diabetes aim for 70 to 130 mg/dL. After meals, the goal is typically under 180 mg/dL. These numbers give enough room to avoid the organ damage that comes with chronically high blood sugar while reducing the chance of dangerous drops.
Blood Sugar Targets During Pregnancy
Pregnancy calls for tighter control because high blood sugar can affect fetal development. The American College of Obstetricians and Gynecologists recommends these targets for pregnant women with diabetes:
- Fasting: below 95 mg/dL
- One hour after eating: below 140 mg/dL
- Two hours after eating: below 120 mg/dL
These apply whether you had diabetes before pregnancy or developed gestational diabetes during it. The tighter fasting target (95 vs. the usual 100) reflects the increased sensitivity needed to protect both mother and baby.
Targets for Children With Diabetes
Children and adolescents with Type 1 diabetes follow similar goals to adults, with some flexibility. The International Society for Pediatric and Adolescent Diabetes recommends spending more than 70% of the day between 70 and 180 mg/dL, with less than 4% of time below 70 mg/dL and less than 1% below 54 mg/dL. Before meals, the target is 70 to 144 mg/dL, and after meals, 70 to 180 mg/dL.
For children using advanced insulin delivery systems, a tighter A1C target of 6.5% or below is reasonable. For everyone else, the goal is 7% or below. These targets always get weighed against quality of life; pushing for tighter control shouldn’t come at the cost of a child’s daily wellbeing.
Adjusted Ranges for Older Adults
Blood sugar targets get looser as people age, especially for those managing multiple health conditions. The reasoning is straightforward: hypoglycemia is more dangerous for older adults. A blood sugar drop that a 35-year-old recovers from easily can cause falls, confusion, or hospitalization in someone who is 80 and frail.
For older adults with significant health issues, a reasonable A1C target may be 8% or below, with fasting levels between 160 and 170 mg/dL. For those in poor health or with cognitive impairment, the goal may be even more relaxed, with an A1C under 8.5% (corresponding to an average glucose around 200 mg/dL). The priority shifts from tight control to preventing both dangerous lows and extreme highs above 350 mg/dL.
Quick Reference
- Normal fasting: below 100 mg/dL
- Normal after eating (2 hours): below 140 mg/dL
- Prediabetes fasting: 100 to 125 mg/dL
- Diabetes fasting: 126 mg/dL or higher
- Low blood sugar (Level 1): 54 to 69 mg/dL
- Severely low (Level 2): below 54 mg/dL
- Diabetes management target: 70 to 180 mg/dL for most of the day
- Pregnancy fasting target: below 95 mg/dL