A normal blood sugar levels chart is a quick reference for the ranges the American Diabetes Association and the National Institute of Diabetes and Digestive and Kidney Diseases use to describe fasting glucose, post-meal glucose, and A1c in nonpregnant adults. The short version: a fasting glucose below 100 mg/dL, a two-hour post-meal reading below 140 mg/dL, and an A1c below 5.7% fall in the range these organizations describe as normal. This article lays out those ranges in plain tables, explains how each test is taken, and addresses the common "by age" question honestly — because the diagnostic thresholds themselves do not shift with age. It is educational only and is not a diagnosis; confirmed testing and interpretation always belong to a clinician.
Key takeaways
- The American Diabetes Association and NIDDK describe normal fasting glucose as below 100 mg/dL, normal two-hour post-meal glucose as below 140 mg/dL, and a normal A1c as below 5.7%.
- Diagnostic thresholds do not change with age; the "normal blood sugar levels by age" question is better answered by noting that care teams may individualize treatment targets for older adults, not the numbers used to diagnose.
- A single reading rarely tells the whole story, because glucose varies with food, activity, stress, illness, and time of day.
- Diagnosis of prediabetes or diabetes requires clinician-confirmed testing, and any chart you read online is a reference, not a substitute for that testing.
Short Answer: What Is a Normal Blood Sugar Level?
For most nonpregnant adults, the American Diabetes Association and NIDDK describe a normal fasting blood glucose as less than 100 mg/dL, a normal glucose value two hours into an oral glucose tolerance test as less than 140 mg/dL, and a normal A1c as less than 5.7%. Those three numbers are the backbone of nearly every normal blood sugar levels chart you will find, and they come from the same organizations that clinicians rely on.
Two things are worth flagging immediately. First, "normal" here refers to diagnostic reference ranges for screening, not to personalized targets someone with diabetes might be given. Second, these ranges apply to results from proper testing, not to a single self-check taken under unknown conditions. A meter reading after a large meal, during illness, or after poor sleep can look different from a clean fasting draw, which is one reason diagnosis is never made from an isolated number. This article is educational, and it does not diagnose anyone.
The Normal Blood Sugar Levels Chart
The table below is the core reference. It compares the normal, prediabetes, and diabetes ranges for the three most common measures, exactly as the American Diabetes Association describes them for nonpregnant adults. Read across each row to see where a given test result would fall.
| Measure | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting plasma glucose | Below 100 mg/dL | 100–125 mg/dL | 126 mg/dL or higher |
| Two-hour OGTT (post-glucose-load) | Below 140 mg/dL | 140–199 mg/dL | 200 mg/dL or higher |
| A1c | Below 5.7% | 5.7%–6.4% | 6.5% or higher |
These ranges come from the American Diabetes Association's diagnostic criteria and are echoed by NIDDK's patient education. A result in the prediabetes column does not mean someone has diabetes, and a single result in the diabetes column is not, by itself, a diagnosis — the American Diabetes Association generally calls for confirmation, which a clinician arranges. The chart tells you which conversation to have, not what your status is.
It also helps to know what each column represents. "Fasting" means no caloric intake for at least eight hours, typically an overnight fast before a morning draw. The OGTT measures glucose two hours after drinking a standardized glucose solution in a clinical setting. A1c reflects average blood glucose over roughly the past two to three months and does not require fasting. Because the three tests measure different things over different windows, they can occasionally disagree, and reconciling them is part of a clinician's job.
Free printable: Download this chart as a one-page PDF to print and keep on the fridge or in a logbook. It includes the diagnostic ranges above, the ADA general treatment targets, and quick notes on how each reading is taken.
Reading the Chart: Normal vs Prediabetes vs Diabetes
The three-column layout is deliberate: it shows that prediabetes sits between clearly normal and clearly diabetic values, describing a range where glucose regulation has started to drift but has not crossed the diabetes threshold. Understanding those bands helps make sense of a lab report without overreading a single figure.
On the fasting scale, a value of 99 mg/dL sits in the normal band while 101 mg/dL sits in the prediabetes band, yet the two are only a couple of points apart and could reflect ordinary day-to-day variation. That closeness is exactly why the American Diabetes Association does not treat one borderline number as definitive and why repeat or confirmatory testing matters. The bands are reference lines, not cliffs.
A1c works the same way. The jump from 5.6% to 5.7% moves a result from the normal band into the prediabetes band, but A1c also has its own measurement variability and can be affected by certain conditions that a clinician accounts for. If you want a deeper look at what different A1c values mean, our guide on what A1c is considered diabetic walks through that single measure in more detail. The point across all three measures is consistent: a normal blood sugar levels chart tells you where a number lands, and a clinician tells you what it means for you.
ADA General Treatment Targets for Adults With Diabetes
There is an important distinction between the diagnostic ranges above and the treatment targets a care team may set for someone who already has diabetes. Diagnostic ranges answer "does this person meet criteria for prediabetes or diabetes?" Treatment targets answer "for a person living with diabetes, what glucose values are we aiming to maintain?" They are not the same numbers, and mixing them up is a common source of confusion.
For many nonpregnant adults with diabetes, the American Diabetes Association describes general treatment targets of roughly 80–130 mg/dL before meals and less than 180 mg/dL about one to two hours after the start of a meal, alongside an A1c goal that is often individualized around a general reference point. These are examples of general targets, not personal instructions — the American Diabetes Association is explicit that targets should be individualized by the care team based on age, other conditions, risk of hypoglycemia, and personal circumstances.
| Target (many nonpregnant adults with diabetes) | ADA general reference |
|---|---|
| Fasting / pre-meal glucose | 80–130 mg/dL |
| Post-meal glucose (1–2 hours after eating) | Less than 180 mg/dL |
That last point matters most for the "by age" question, which comes up next. Because targets are individualized, an older adult with several health conditions may be given different, often less stringent, targets than a younger adult — but the diagnostic thresholds that define diabetes do not change with age. If you are working on your own morning numbers, our guide on how to lower fasting blood sugar naturally covers lifestyle levers that sit alongside, never replace, a care team's plan.
Normal Blood Sugar Levels by Age: What Actually Changes
Search interest in "normal blood sugar levels by age" is high, and the honest answer surprises many people: the American Diabetes Association's diagnostic thresholds are the same for a 25-year-old and a 75-year-old. A fasting glucose of 126 mg/dL or higher meets the diabetes threshold regardless of age, and an A1c below 5.7% is described as normal at any adult age. There is no separate "normal chart" that loosens the diagnostic numbers as people get older.
What can change with age is the treatment target a clinician sets for a person who already has diabetes. Guidelines recognize that a fit, otherwise-healthy older adult and an older adult with multiple chronic conditions may warrant different goals. In some cases, care teams set less stringent targets for older adults specifically to reduce the danger of low blood sugar, which can be more harmful than modestly elevated readings in that population. That is individualization of targets, not a change in what defines diabetes.
So when a chart online promises "normal blood sugar by age," treat the diagnostic thresholds it shows as age-independent and be cautious about any table implying the diagnosis itself shifts with birthdays. The nuance lives entirely on the treatment side, and it is set by a clinician who knows the whole person. For a related everyday question, our explainer on what your blood sugar should be when you wake up puts the fasting number in daily context.
How and When Readings Are Taken
The same person can produce very different glucose numbers within a single day, so knowing which test a number came from is essential to reading it against any chart. Each common measurement captures a different moment or window.
A fasting reading is taken after at least eight hours without calories, usually first thing in the morning. It reflects baseline glucose when no recent meal is influencing the result, which is why it anchors both the diagnostic chart and many treatment targets. A post-meal reading — often checked one to two hours after starting to eat — shows how the body handled that particular meal, and it is the basis for the OGTT's standardized two-hour measurement.
A random (or casual) glucose is taken at any time without regard to meals; on its own it is less useful for diagnosis, though a very high random value with symptoms can prompt further testing. Finally, A1c does not require fasting and estimates average glucose over the prior two to three months, smoothing out day-to-day swings. Because these tests look at different time frames, the American Diabetes Association uses several together rather than relying on one, and interpreting the combination is a clinical task.
Why a Single Reading Varies So Much
It is normal for glucose to move throughout the day, and a single number should never be read as a verdict. Understanding the ordinary sources of variation prevents the twin errors of false alarm and false reassurance.
Food is the most obvious driver: the size, composition, and timing of a meal all shift post-meal glucose. But many other factors move readings too. Physical activity can lower glucose, while stress hormones, illness, pain, and poor sleep can raise it. Time of day matters as well — many people see higher glucose in the early morning because of normal hormonal rhythms, a pattern our guide on why blood sugar is high in the morning explains in detail. Even hydration, caffeine, and the accuracy of a home meter and its strips can nudge a result.
Because of all this, one reading outside a chart's normal band is a reason to keep observing and to talk with a clinician, not to self-diagnose. Trends across several readings under known conditions are far more informative than any isolated check. This is also why the diagnostic process relies on standardized, repeated, or confirmed testing rather than a single glucometer glance.
Getting a Confirmed Diagnosis
A normal blood sugar levels chart is a screening reference, and screening is not diagnosis. The American Diabetes Association describes a diagnostic process in which results are obtained under proper conditions and, in the absence of clear symptoms of very high glucose, generally confirmed with repeat testing before a diagnosis of diabetes is made. That structure exists precisely because single readings vary.
In practice, a clinician may order a fasting glucose, an A1c, or an OGTT, interpret the results together, and arrange a confirming test when needed. They also account for factors that can affect specific tests — for instance, certain conditions can make A1c less reliable — and choose the measure that fits the individual. None of this can be replicated by reading a chart at home, which is the whole reason diagnosis belongs with a clinician.
If your numbers land in the prediabetes band, that finding is actionable rather than alarming: it is the window where lifestyle changes have the most documented impact, and a care team can help you build a plan. Understanding where a number sits on the chart is a useful first step, but confirmation and next steps are clinical decisions made with you.
Frequently Asked Questions
What is a normal blood sugar level for adults?
The American Diabetes Association and NIDDK describe a normal fasting blood glucose for nonpregnant adults as less than 100 mg/dL, a normal two-hour value on an oral glucose tolerance test as less than 140 mg/dL, and a normal A1c as less than 5.7%. These are diagnostic reference ranges used for screening, not personalized targets for someone who already has diabetes. A result outside the normal band is a reason to talk with a clinician rather than a diagnosis on its own, because glucose varies and diagnosis requires confirmed testing.
Do normal blood sugar levels change with age?
The diagnostic thresholds that define normal, prediabetes, and diabetes do not change with age. A fasting glucose of 126 mg/dL or higher meets the diabetes threshold and an A1c below 5.7% is described as normal at any adult age. What can change with age is the treatment target a clinician sets for a person who already has diabetes, since care teams may individualize goals for older adults, sometimes setting less stringent targets to reduce the risk of low blood sugar. That is individualization of targets, not a change in the numbers used to diagnose.
What blood sugar level is considered prediabetes?
According to the American Diabetes Association, prediabetes corresponds to a fasting glucose of 100 to 125 mg/dL, a two-hour oral glucose tolerance test value of 140 to 199 mg/dL, or an A1c of 5.7% to 6.4%. These values sit between clearly normal and clearly diabetic ranges and describe glucose regulation that has started to drift without crossing the diabetes threshold. A prediabetes result is not a diabetes diagnosis, and it is best confirmed and interpreted by a clinician who can help build a plan.
What A1c level means diabetes?
The American Diabetes Association describes an A1c of 6.5% or higher as meeting the threshold for diabetes, while 5.7% to 6.4% falls in the prediabetes range and below 5.7% is described as normal. A1c reflects average glucose over roughly the past two to three months and does not require fasting. Because certain conditions can make A1c less reliable and because a single result may need confirmation, diagnosis based on A1c is made by a clinician who interprets it alongside your other results.
What is a normal blood sugar level after eating?
On the diagnostic scale, a normal two-hour value during an oral glucose tolerance test is less than 140 mg/dL. For many nonpregnant adults who already have diabetes, the American Diabetes Association describes a general treatment target of less than 180 mg/dL about one to two hours after starting a meal, though targets are individualized by the care team. Post-meal readings vary with the size and composition of the meal, activity, and other factors, so a single high reading is not a diagnosis and is best discussed with a clinician.
Why is my blood sugar different every time I check it?
Glucose naturally moves through the day, so variation between checks is expected. Food, physical activity, stress, illness, pain, poor sleep, time of day, hydration, caffeine, and even meter and strip accuracy can all shift a reading. Many people also see higher glucose in the early morning because of normal hormonal rhythms. Because of this variability, trends across several readings taken under known conditions are far more informative than any single check, and one number outside a chart's normal band is a reason to keep observing and talk with a clinician.
Can I diagnose diabetes myself using a blood sugar chart?
No. A blood sugar levels chart is a screening reference, not a diagnostic tool. The American Diabetes Association describes a diagnostic process that uses results obtained under proper conditions and, in the absence of clear symptoms of very high glucose, generally confirmed with repeat testing. A clinician also accounts for factors that can affect specific tests and chooses the right measure or combination for the individual. Reading where a number falls on a chart is a useful first step, but confirmation and interpretation belong with a clinician.
How often should adults check their blood sugar?
There is no single answer that fits everyone, because testing frequency depends on whether a person has diabetes, prediabetes, or no diagnosis, and on the plan their clinician sets. For screening, the American Diabetes Association recommends discussing testing with a clinician based on individual risk factors rather than a fixed schedule. For someone living with diabetes, how often to check is part of an individualized plan, and any monitoring routine should be set with a care team rather than based on a general chart.
References
- American Diabetes Association: Diagnosis
- NIDDK: Diabetes Tests & Diagnosis
- FDA: Blood Glucose Monitoring Devices
Next Steps
A normal blood sugar levels chart is a helpful reference: it shows that the American Diabetes Association and NIDDK describe normal fasting glucose as below 100 mg/dL, normal two-hour post-meal glucose as below 140 mg/dL, and a normal A1c as below 5.7%, with clear prediabetes and diabetes bands above those. The diagnostic thresholds stay the same across adulthood, while treatment targets can be individualized by a care team, especially for older adults. Wherever your numbers land, confirmed testing and interpretation belong with a clinician — a chart points you toward the right conversation, not a diagnosis.
If you're ready to build the daily habits that support steadier blood sugar alongside any guidance from your care team, the Done With Diabetes™ program, a holistic approach to type 2 diabetes, offers practical support on nutrition, movement, sleep, and daily routines. Get started with Vynleads to take the next step.