Normal Blood Sugar Levels Chart: Fasting, After Eating, and by Age

Search for “normal blood sugar” and you will find a dozen charts that disagree. The confusion comes from mixing three different things: the cut-offs used to diagnose diabetes, the targets doctors set for people who already have it, and the ranges people see on a continuous glucose monitor. This guide separates them, shows each one in mg/dL and mmol/L, and explains what a single reading can and cannot tell you.

Quick answer: For adults, a fasting plasma glucose under 100 mg/dL (5.6 mmol/L) and an A1C under 5.7% are in the normal range. Fasting glucose of 100 to 125 mg/dL, A1C of 5.7% to 6.4%, or a 2-hour glucose tolerance result of 140 to 199 mg/dL falls in the prediabetes range. Fasting glucose of 126 mg/dL or higher, A1C of 6.5% or higher, or a 2-hour result of 200 mg/dL or higher falls in the diabetes range. For people who have diabetes, the ADA suggests a before-meal target of 80 to 130 mg/dL and a peak under 180 mg/dL, 1 to 2 hours after a meal begins. This is education, not a diagnosis.

The diagnostic chart: normal, prediabetes, and diabetes

These are the criteria used by the American Diabetes Association for adults. Fasting means no calories for at least eight hours. The glucose tolerance test (OGTT) measures glucose two hours after a 75 g glucose drink. Sources: Wisconsin Department of Health Services summary of ADA criteria and the Johns Hopkins Diabetes Guide.

Two points matter more than the numbers themselves. First, only one of these tests has to land in a range for a clinician to take notice, but diagnosing diabetes without clear symptoms generally requires two abnormal results, either from the same sample or from two separate samples. Second, the tests can disagree. Your fasting glucose can be normal while your A1C is not, which is one reason we wrote A1C vs fasting glucose vs OGTT and why A1C can be wrong.

Blood sugar targets for people who have diabetes

A diagnosis threshold answers “is this diabetes?” A target answers “what should I aim for now that I have it?” The ADA glycemic targets summary lists these for most non-pregnant adults:

These targets come from the 2023 edition of the Standards of Care summarized in that document, and they are individualized. A clinician may set a tighter or looser goal depending on your age, your medicines, your history of low blood sugar, and what else is going on in your health.

Normal blood sugar by age

Many charts online show a separate row for every decade, which gives the impression that the cut-offs move with age. For adults, the diagnostic cut-offs above do not change as you get older. What does change is how aggressively a clinician aims to treat.

I have not listed ranges for children or pregnancy on purpose. Those targets are set by the care team and vary, and a wrong number from a web page is worse than no number.

Fasting, after eating, and the time of day

Glucose is not a fixed number. It moves with meals, sleep, stress, illness, and activity. That is why the charts above specify when to measure.

• Fasting means at least eight hours without calories. It is the cleanest comparison point, and the one the diagnostic cut-offs use.
• One to two hours after the start of a meal is when the ADA suggests checking a post-meal peak. Count from the first bite, not the last.
• Random readings are hard to interpret unless you know what you ate and when. Our post-meal glucose tracker helps you log the meal alongside the number.
• Morning readings can run higher than bedtime readings for reasons unrelated to dinner. See the dawn phenomenon guide.

What about CGM ranges?

A continuous glucose monitor shows a glucose line instead of a few points, so the useful question changes from “what was my number?” to “how much of my day was spent in range?” A commonly used CGM target range is 70 to 180 mg/dL (3.9 to 10.0 mmol/L). People without diabetes generally spend most of the day inside it, with short rises after meals. We cover this in detail in normal CGM glucose range without diabetes, and our CGM reading guide shows how to spot sensor artifacts. If you are choosing a sensor, start with which CGM is right for your goal.

Keep in mind that over-the-counter CGMs are meant for wellness and pattern-finding. They are not diagnostic tools, and a CGM average does not replace a laboratory test. See CGM vs A1C for how the two relate.

A worked example

Suppose a 52-year-old adult has fasting labs that show a glucose of 108 mg/dL and an A1C of 5.9%.

1. Convert units. 108 mg/dL divided by 18 is 6.0 mmol/L.
2. Place each result. 108 mg/dL is in the 100 to 125 range, and 5.9% is in the 5.7% to 6.4% range. Both fall in the prediabetes range.
3. Do not stop there. One set of labs is a starting point. Ask the clinician whether to repeat the tests, add a glucose tolerance test, or look at related markers. Our A1C 5.7 guide and prediabetes guide explain what usually happens next.
4. Look at the lifestyle levers. Meals, movement, sleep, and weight all influence these numbers. Start with diet for prediabetes and exercise and glucose.

This example is arithmetic and classification only. It is not a treatment recommendation.

Reading your own numbers: a short checklist

Common mistakes

• Treating a chart as a diagnosis. Only a clinician can diagnose, and it usually takes two abnormal results.
• Comparing a post-meal reading with a fasting cut-off. They answer different questions.
• Using an adult chart for a child or a pregnancy. Those targets are different.
• Chasing a single reading. Look at the pattern across several days.
• Mixing units. A “7” in mmol/L is not a “7” in mg/dL.
• Loosening or tightening a target on your own. Targets are personal, and changes belong in a conversation with your care team.

Questions to bring to your appointment

• Which of my results are in the normal, prediabetes, or diabetes range, and should any be repeated?
• Does my A1C match my fasting glucose, or is there a reason they might differ?
• What targets are right for me, given my age, medicines, and health history?
• When should I check at home, and what should I do with the numbers?
• Would a glucose tolerance test or a CGM add anything for me?

Frequently asked questions

What is a normal blood sugar level?

For adults, the standard cut-offs say a fasting plasma glucose under 100 mg/dL (5.6 mmol/L) and an A1C under 5.7% are in the normal range. A 2-hour result under 140 mg/dL (7.8 mmol/L) on a glucose tolerance test is also normal. Numbers outside these are not a diagnosis by themselves, because diabetes needs confirmation with repeat or second testing.

What blood sugar is normal 2 hours after eating?

After a 75 g glucose drink in a lab test, under 140 mg/dL is normal and 140 to 199 mg/dL is in the prediabetes range. For people who already have diabetes, the ADA suggests a peak of under 180 mg/dL, measured 1 to 2 hours after the start of a meal. Real meals vary, so one reading is a snapshot rather than a verdict.

What is a normal fasting blood sugar by age?

The adult diagnostic cut-offs are the same at every adult age: under 100 mg/dL is normal, 100 to 125 is prediabetes, and 126 or higher is in the diabetes range. What changes with age is the treatment target, which a clinician may relax for older adults who have other health conditions or a higher risk of lows. Children are handled by their pediatric team and should not use an adult chart.

Is 140 mg/dL after eating bad?

A single 140 mg/dL reading is not a diagnosis. On a formal glucose tolerance test, a 2-hour value of 140 to 199 mg/dL falls in the prediabetes range, but a casual reading after a real meal does not compare directly with that test. If you see it often, bring your log to a clinician and ask whether fasting glucose, A1C, or a tolerance test makes sense.

How do I convert mg/dL to mmol/L?

Divide the mg/dL value by 18. For example, 126 mg/dL is about 7.0 mmol/L and 100 mg/dL is about 5.6 mmol/L. To go the other way, multiply mmol/L by 18.

Can I diagnose diabetes from a home meter or CGM?

No. A diagnosis rests on laboratory testing, and in the absence of clear symptoms with very high glucose it generally needs two abnormal results, either from the same sample or from two separate samples. Home meters and over-the-counter CGMs are useful for patterns, but they are not diagnostic tools.

How often should I check my blood sugar?

It depends on your diagnosis, medicines, and goals. Someone on insulin may check several times a day, while someone without diabetes may never need a home meter. Ask your care team what schedule makes sense and what you should do with the numbers.

About the author: Charles Kirkland is the founder of Metabolic Clarity Labs and author of The Journey Back. He is not a physician. This is general education, not a medically reviewed treatment plan.

Sources checked October 31, 2026. Discuss personal decisions with a qualified clinician. Do not start, stop, or change prescribed treatment based on this article.