Normal Blood Sugar Levels: Chart by Age, mg/dL & mmol/L

For most non-pregnant adults, the American Diabetes Association (ADA) considers a normal fasting blood sugar to be under 100 mg/dL (5.6 mmol/L), and a value below 140 mg/dL (7.8 mmol/L) two hours after eating. If you already live with diabetes, common ADA targets are 80–130 mg/dL (4.4–7.2 mmol/L) before meals and under 180 mg/dL (10.0 mmol/L) about one to two hours after a meal. These are general reference points — individual targets vary, and your care team sets yours.

The chart and sections below break down what those numbers mean, how they shift by context and age, and how to read the same reading in both mg/dL and mmol/L.

Normal blood sugar levels chart (mg/dL & mmol/L)

The table below summarizes the ADA thresholds most people ask about. Diabetes diagnosis is based on standardized tests interpreted by a clinician — use this as a reference, not a diagnosis.

Diagnostic cut-offs generally need to be confirmed on a separate day unless symptoms are clearly present. A1C is also used for diagnosis and monitoring; see our A1C chart and conversion guide for how A1C maps to an average glucose.

Normal blood sugar by age

Many people search for a “blood sugar levels by age” chart, expecting a different row for every decade of life. In reality, the ADA fasting and post-meal ranges above apply to adults broadly rather than shifting by age. Age matters less as a fixed cut-off and more in how goals are personalized around it.

For older adults — especially those with several other health conditions, a history of severe lows, or difficulty recognizing symptoms of hypoglycemia — clinicians often set slightly higher, less strict targets. The reasoning is safety: a very tight goal can raise the risk of dangerous low blood sugar, which for an older person may carry more serious consequences than a modestly elevated reading. So an A1C or glucose target that is right for a healthy 30-year-old may deliberately be relaxed for an 80-year-old with heart or kidney disease.

Children and adolescents with diabetes follow separate, pediatric targets, and pregnant people have their own tighter ranges. For pregnancy specifically, see our gestational diabetes targets. The practical takeaway is simple: treat the reference ranges as a starting point, and let your doctor tailor them to your age, overall health, and treatment. If you see an online “by age” chart with precise numbers for every age band, be cautious — those are rarely the actual ADA thresholds.

Normal blood sugar for adults

For a non-pregnant adult without diabetes, the ADA describes normal as under 100 mg/dL (5.6 mmol/L) fasting and under 140 mg/dL (7.8 mmol/L) two hours after a glucose load. Fasting simply means no food or caloric drinks for at least eight hours, which is why fasting readings are usually taken first thing in the morning before breakfast.

Prediabetes sits in the middle band — a fasting result of 100–125 mg/dL (5.6–6.9 mmol/L). It is a signal, not a sentence, and is often improved or reversed with changes to diet, activity, sleep, and weight, together with regular follow-up. A fasting result of 126 mg/dL (7.0 mmol/L) or higher, confirmed by repeat testing or clear symptoms, points to diabetes and warrants a conversation with your doctor rather than self-diagnosis. Because a single reading can be thrown off by illness, stress, or an unnoticed snack, clinicians look at patterns over time and confirm diagnostic values on a separate day.

Normal blood sugar for people with diabetes

If you already manage diabetes, “normal” is defined by your personal targets rather than the general population ranges. ADA commonly cites 80–130 mg/dL (4.4–7.2 mmol/L) before meals and under 180 mg/dL (10.0 mmol/L) after meals for many adults, but these are examples. Your numbers depend on your type of diabetes, medications, age, and other conditions. Talk to your doctor before changing how you interpret your readings.

Reading your numbers in mmol/L

Some countries report glucose in mg/dL (common in the United States) and others in mmol/L (common in the UK, Canada, Australia, and much of Europe). They describe the exact same thing and are interchangeable with a single conversion factor: divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL.

A few worked examples: 100 mg/dL ÷ 18 ≈ 5.6 mmol/L, 126 mg/dL ÷ 18 = 7.0 mmol/L, and 180 mg/dL ÷ 18 = 10.0 mmol/L. Going the other way, 4.4 mmol/L × 18 ≈ 80 mg/dL. Mixing up the units is a common source of confusion — a value like “7” is alarmingly high in mmol/L terms but perfectly normal if it were mg/dL, so always confirm which unit a number is in before reacting to it. If you compare a lab result with your home log, make sure both use the same unit. Our mmol/L to mg/dL converter and chart walks through the math with more examples.

When a number needs urgent attention

Very low blood sugar (hypoglycemia), often around 70 mg/dL (3.9 mmol/L) or below, and very high readings can be dangerous. If you have symptoms of severe low blood sugar (confusion, seizures, loss of consciousness) or dangerously high glucose with symptoms like vomiting, rapid breathing, or fruity-smelling breath, treat it as an emergency and seek medical help right away. This article is general information and cannot tell you your personal danger thresholds — your care team can.

Seeing your own pattern with GlucoLog

A single reading is a snapshot; your pattern is the story. Where the chart above shows what is typical, your own log shows what is happening to you — and that comparison is far more useful to you and your doctor than any generic table.

GlucoLog is a logging and analysis tool — it does not measure your blood sugar and is not a glucose meter or medical device. You enter each reading you take on a large-button numpad in either mg/dL or mmol/L, then tag it with meal context such as fasting, before meal, after meal, or bedtime. Because the readings are labeled, the after-eating spikes and morning highs described in this article become easy to spot across 7-day, 30-day, 90-day, and longer trend charts, and a time-in-range view shows how often your numbers land where you want them. When it is time for an appointment, you can export a compact or detailed PDF report — or a CSV file — to bring your doctor a clear summary instead of a pile of loose numbers. For the day-to-day routine, our guide to tracking blood sugar shows how meal tags make these patterns visible.

Frequently asked questions

What is a normal blood sugar level?

For adults without diabetes, the ADA considers under 100 mg/dL (5.6 mmol/L) fasting and under 140 mg/dL (7.8 mmol/L) two hours after eating to be normal. Individual targets vary, so confirm what “normal” means for you with your doctor.

Is 140 mg/dL after eating normal?

A value under 140 mg/dL (7.8 mmol/L) two hours after a glucose load is in the normal range for people without diabetes. For many people managing diabetes, a common ADA post-meal target is under 180 mg/dL (10.0 mmol/L). See our guide on blood sugar after eating for the 1-, 2-, and 3-hour picture.

Does normal blood sugar change with age?

The general reference ranges apply broadly to adults. What often changes with age is how strict the targets are — older adults or those with other conditions may be given slightly higher goals to avoid dangerous lows. Your care team decides.