Normal fasting blood sugar is under 100 mg/dL. Prediabetes is 100-125. Diabetes is 126+. A1C under 5.7% is normal. These ranges shift slightly with age — older adults naturally have higher baselines.
Written by Ash K · Last updated: June 2026 · Sources cited below
Normal blood sugar ranges shift with age — what's healthy for a child differs from what's healthy for an adult over 65. This guide provides the complete blood sugar level range chart by age group, covering fasting, post-meal, and A1C values with ADA and WHO reference ranges.
Understanding your numbers in context of your age group is the first step toward knowing whether your glucose metabolism is healthy, trending toward prediabetes, or needs medical attention.
Key Takeaway: Fasting blood sugar below 100 mg/dL is normal for most adults. 100–125 mg/dL is prediabetes. 126+ mg/dL (confirmed on two tests) is diabetes per ADA criteria. Children and older adults have slightly different thresholds and clinical considerations — see the full chart below.
| Age Group | Fasting (mg/dL) | 2 hr Post-Meal (mg/dL) | A1C (%) | Notes |
|---|---|---|---|---|
| Children (6–12 years) | 70–100 | Below 140 | Below 5.7% | ADA pediatric guidelines; wider swings normal |
| Teens (13–19 years) | 70–100 | Below 140 | Below 5.7% | Puberty can cause temporary insulin resistance |
| Adults (20–59 years) | 70–100 (normal) | Below 140 (normal) | Below 5.7% (normal) | ADA standard adult thresholds |
| Adults — prediabetes | 100–125 | 140–199 | 5.7–6.4% | Lifestyle changes can reverse progression |
| Adults — diabetes | 126+ | 200+ | 6.5%+ | Requires confirmation with repeat testing |
| Seniors (60+ years) | 70–130 (often relaxed) | Below 180 (often relaxed) | Below 7.0–7.5% | Tighter targets may increase hypoglycemia risk |
| Pregnancy (GDM screening) | Below 92 (IADPSG) | Below 153 (1-hr OGTT) | Not used for GDM dx | Oral glucose tolerance test is the standard |
Sources: ADA Standards of Care 2024; WHO Diagnostic Criteria; IADPSG Consensus Panel.
Blood Sugar Ranges — Normal vs Prediabetes vs Diabetes
Children's blood sugar is monitored differently from adults. The ADA pediatric guidelines recommend:
Fasting: 70–100 mg/dL — same as adults.
Random/post-meal: Below 140 mg/dL — though children's blood sugar fluctuates more than adults' because of irregular eating patterns, activity bursts, and growth hormone effects.
Note: Blood sugar in children is harder to interpret because of natural variability. A child with a fasting glucose of 105 on one morning may read 88 the next morning — both can be normal. If your child's pediatrician is concerned, they'll order an A1C or oral glucose tolerance test rather than relying on a single fasting value.
Type 1 diabetes (autoimmune destruction of insulin-producing beta cells) is the most common form in children, unlike type 2 which dominates in adults. Symptoms include sudden weight loss, excessive thirst, frequent urination, and fatigue. These warrant immediate medical evaluation.
Typical Fasting Glucose by Age Decade
Insulin sensitivity declines with age. After 45, the risk of prediabetes and type 2 diabetes increases progressively. This is driven by declining muscle mass (muscle is the primary glucose disposal site), increasing adiposity, and age-related changes in insulin secretion.
Older adults (65+) have relaxed targets. The ADA recommends less stringent glucose targets for older adults — particularly those with limited life expectancy, multiple comorbidities, or cognitive impairment — because tight glucose control increases hypoglycemia risk. Hypoglycemia in seniors can cause falls, fractures, confusion, and cardiac events.
Pregnancy changes everything. Gestational diabetes uses different diagnostic criteria (IADPSG consensus): fasting ≥92 mg/dL, 1-hour OGTT ≥180 mg/dL, or 2-hour OGTT ≥153 mg/dL. A1C is not used for gestational diabetes diagnosis because it underestimates glycemia during pregnancy.
Tip: If you're over 45, haven't had a blood sugar test in the past 3 years, and have any risk factors (overweight, family history, sedentary lifestyle), request a fasting glucose or A1C at your next checkup. Prediabetes is reversible with lifestyle changes — but only if you know about it. For A1C interpretation, see our A1C to blood sugar converter.
Consistently above 100 mg/dL fasting — suggests insulin resistance developing. Warrants A1C testing and lifestyle assessment.
Above 126 mg/dL fasting on two separate tests — meets ADA criteria for diabetes diagnosis.
Random blood sugar above 200 mg/dL with symptoms (thirst, frequent urination, unexplained weight loss) — warrants immediate medical evaluation.
Below 70 mg/dL — hypoglycemia. May cause shakiness, confusion, sweating, rapid heartbeat. If you're on diabetes medication, this requires immediate treatment (15g fast-acting carbohydrate).
Warning: Blood sugar interpretation requires clinical context. A single reading can be affected by recent food, stress, illness, medications, and testing method (glucometer vs. lab). Your provider interprets glucose alongside A1C, symptoms, family history, and other metabolic markers — not in isolation.
Bottom Line: Normal fasting blood sugar is 70–100 mg/dL for most ages. Children, seniors, and pregnant individuals have modified targets. If your numbers fall in the prediabetes range (100–125 fasting, A1C 5.7–6.4%), the evidence strongly supports that lifestyle changes — moderate weight loss, regular exercise, dietary adjustments — can prevent or delay progression to diabetes.
What is a normal blood sugar level for my age?
For adults 20–59: fasting 70–100 mg/dL, A1C below 5.7%. For seniors 60+: targets are often relaxed to 70–130 fasting and A1C below 7.0–7.5% to reduce hypoglycemia risk. For children: 70–100 fasting with wider post-meal variation accepted.
What is a dangerous blood sugar level?
Below 54 mg/dL is clinically significant hypoglycemia (medical emergency for diabetics on medication). Above 300 mg/dL with symptoms warrants urgent medical attention. Above 600 mg/dL is a medical emergency (diabetic hyperosmolar syndrome).
Does blood sugar increase with age?
Average fasting blood sugar tends to increase modestly with age due to declining insulin sensitivity and muscle mass. This doesn't mean diabetes is inevitable — regular exercise and healthy weight maintenance can maintain normal glucose metabolism at any age.
This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider with questions about your health.