A blood sugar chart can be useful, but only when you know what kind of glucose result you are looking at. A fasting laboratory glucose, a reading from your home meter after dinner, an HbA1c result and a two-hour glucose tolerance test are not interchangeable.
I usually start by asking a simple question: When was the glucose measured? The same number can have a different meaning depending on whether you were fasting, had just eaten, were undergoing a standardized glucose tolerance test, or already have diabetes and are monitoring treatment.
For adults who have not been diagnosed with diabetes, normal diagnostic laboratory results generally include:
For many nonpregnant adults who already have diabetes, commonly used treatment goals include:
Diagnostic ranges and diabetes treatment targets are different concepts. Do not use one table in place of the other.
This chart brings the key blood sugar ranges together in one place for easier comparison. It also separates diagnostic values from treatment targets, since these numbers are used for different purposes and should not be interpreted in the same way.
| Test or Situation | Common Reference Range | What It Means |
|---|---|---|
| Fasting plasma glucose — laboratory test | ≤99 mg/dL ≤5.5 mmol/L |
Normal diagnostic range |
| Fasting plasma glucose — laboratory test | 100–125 mg/dL 5.6–6.9 mmol/L |
Prediabetes range |
| Fasting plasma glucose — laboratory test | ≥126 mg/dL ≥7.0 mmol/L |
Diabetes diagnostic range when diagnostic requirements are met |
| 2-hour 75-g OGTT | ≤139 mg/dL <7.8 mmol/L |
Normal diagnostic range |
| 2-hour 75-g OGTT | 140–199 mg/dL 7.8–11.0 mmol/L |
Impaired glucose tolerance / prediabetes range |
| 2-hour 75-g OGTT | ≥200 mg/dL ≥11.1 mmol/L |
Diabetes diagnostic range when diagnostic requirements are met |
| Before meals — many adults with diabetes | 80–130 mg/dL 4.4–7.2 mmol/L |
Common treatment target, not a diagnostic range |
| Peak post-meal — many adults with diabetes | <180 mg/dL <10.0 mmol/L |
Common treatment target, usually assessed 1–2 hours after starting the meal |
| Low glucose alert level | <70 mg/dL <3.9 mmol/L |
Clinically important hypoglycemia in people with diabetes |
| Level 2 hypoglycemia | <54 mg/dL <3.0 mmol/L |
Requires immediate action |
The diagnostic values above apply to nonpregnant individuals. Pregnancy has different diagnostic criteria and treatment targets.
If you are trying to understand whether a laboratory result falls into the normal, prediabetes or diabetes range, the following chart will shows how the main laboratory tests are used to distinguish between normal glucose levels, prediabetes, and diabetes. The interpretation depends on the specific test performed, so it is important to compare your result with the correct diagnostic range.
| Diagnostic Test | Normal | Prediabetes | Diabetes Range |
|---|---|---|---|
| Fasting plasma glucose | ≤99 mg/dL | 100–125 mg/dL | ≥126 mg/dL |
| HbA1c | <5.7% | 5.7–6.4% | ≥6.5% |
| 2-hour plasma glucose during 75-g OGTT | ≤139 mg/dL | 140–199 mg/dL | ≥200 mg/dL |
| Random plasma glucose | Not used to define a normal screening range | Not used to diagnose prediabetes | ≥200 mg/dL with classic symptoms of hyperglycemia or hyperglycemic crisis |
In the absence of unequivocal hyperglycemia, a diabetes diagnosis generally requires confirmation with repeat or additional appropriate testing.
For a deeper explanation of each test, see Blood Tests for Diabetes .
Once diabetes has already been diagnosed, we use glucose numbers differently. We are no longer asking whether a result diagnoses diabetes. We are asking whether treatment is keeping glucose within an appropriate and safe range.
| Measurement | Common Goal for Many Nonpregnant Adults |
|---|---|
| HbA1c | <7.0% |
| Before meals | 80–130 mg/dL (4.4–7.2 mmol/L) |
| Peak after meals | <180 mg/dL (<10.0 mmol/L) |
These are general treatment goals. A person's individual target may be higher or lower depending on hypoglycemia risk, medications, pregnancy, kidney disease, other medical conditions, cognitive or functional status, and overall treatment burden.
Treatment goals are not identical for every person with diabetes. Factors such as hypoglycemia risk, medications, kidney function, other medical conditions, and overall treatment burden can influence what is considered an acceptable blood glucose level for an individual patient.
Age is another factor that can influence treatment decisions. The diagnostic thresholds themselves do not simply rise with age, but blood sugar targets in older adults may be adjusted according to overall health, functional status, and the risk of hypoglycemia.
This is one of the easiest areas to misunderstand because two very different measurements are often placed in the same chart.
| Measurement | How to Interpret It |
|---|---|
| 2-hour 75-g OGTT | This is a standardized diagnostic test. A 2-hour result of 140–199 mg/dL is the impaired glucose tolerance range, while ≥200 mg/dL is within the diabetes diagnostic range. |
| Home glucose after an ordinary meal — person without diagnosed diabetes | The result depends on the meal, exact timing, activity, insulin sensitivity and other factors. An ordinary post-meal home reading should not be classified as prediabetes or diabetes by applying the OGTT cutoffs. |
| Peak post-meal glucose — person with diabetes | For many nonpregnant adults, a common treatment target is <180 mg/dL, generally assessed 1–2 hours after the beginning of the meal. |
When someone tells me, “My blood sugar was 160 after eating,” I do not immediately call the result normal, prediabetes or diabetes.
I first want to know when the glucose was measured, what the person ate, whether the reading came from a home meter or laboratory, whether diabetes has already been diagnosed, and whether this is an isolated number or a repeated pattern.
The context often changes the interpretation.
For people with diabetes, especially those using insulin or medicines that can cause hypoglycemia, low glucose deserves particular attention.
| Glucose Level | Classification | What It Means |
|---|---|---|
| <70 to ≥54 mg/dL <3.9 to ≥3.0 mmol/L |
Level 1 hypoglycemia | Clinically important low glucose. Follow your prescribed hypoglycemia treatment plan. |
| <54 mg/dL <3.0 mmol/L |
Level 2 hypoglycemia | A more serious low glucose level that requires immediate action. |
| Severe event requiring help from another person | Level 3 hypoglycemia | Defined by impaired mental or physical functioning requiring assistance, regardless of the exact glucose number. |
Symptoms of hypoglycemia can include shaking, sweating, hunger, weakness, dizziness, irritability, rapid heartbeat, difficulty concentrating or confusion.
HbA1c does not show your glucose at this exact moment. It reflects longer-term glucose exposure over approximately the previous two to three months.
| HbA1c | Estimated Average Glucose (mg/dL) | Estimated Average Glucose (mmol/L) |
|---|---|---|
| 5.7% | 117 | 6.5 |
| 6.0% | 126 | 7.0 |
| 6.5% | 140 | 7.8 |
| 7.0% | 154 | 8.6 |
| 8.0% | 183 | 10.2 |
| 9.0% | 212 | 11.8 |
| 10.0% | 240 | 13.3 |
| 11.0% | 269 | 14.9 |
| 12.0% | 298 | 16.6 |
These values are estimates. Two people with the same HbA1c may still have very different daily glucose patterns, including different highs, lows and glucose variability.
Have your own result? Use our: HbA1c to Estimated Average Glucose Calculator .
For a full explanation of the test, see: HbA1c Explained .
Glucose is commonly reported in mg/dL in the United States and in mmol/L in many other countries.
| mg/dL | Approximate mmol/L |
|---|---|
| 54 | 3.0 |
| 70 | 3.9 |
| 80 | 4.4 |
| 90 | 5.0 |
| 99 | 5.5 |
| 100 | 5.6 |
| 126 | 7.0 |
| 130 | 7.2 |
| 140 | 7.8 |
| 180 | 10.0 |
| 200 | 11.1 |
| 250 | 13.9 |
| 300 | 16.7 |
For any value not shown in this table, use our: Blood Sugar mg/dL ↔ mmol/L Converter .
A single glucose reading can be useful, but I rarely interpret it without context.
Ask:
A single glucose value can be difficult to interpret without knowing when it was measured and what was happening around that time. The meaning of an individual blood sugar reading depends on factors such as fasting status, meal timing, medications, symptoms, and whether diabetes has already been diagnosed.
A glucose reading around 250 mg/dL or higher is well above the usual treatment range for most people with diabetes, but the appropriate response depends on the situation.
If you already have diabetes, follow your prescribed high-glucose or sick-day plan. Depending on your diabetes type, treatment and clinical instructions, this may include repeating the glucose measurement, checking ketones, taking prescribed correction insulin and maintaining appropriate hydration.
People using insulin, especially those with type 1 diabetes, should take persistent high glucose seriously because insulin deficiency can lead to diabetic ketoacidosis.
Very high or very low glucose becomes more concerning when it is persistent, accompanied by significant symptoms, or associated with conditions such as dehydration, vomiting, confusion, difficulty breathing, or loss of consciousness. The warning signs that may require urgent medical attention are outlined in our guidance on dangerous blood sugar levels .
The laboratory thresholds used to diagnose prediabetes and diabetes do not simply become higher because an adult gets older.
What may change is the treatment target for someone who already has diabetes. Older adults with frailty, cognitive or functional limitations, severe medical conditions or substantial risk of hypoglycemia may need more individualized goals.
Age can become particularly important when treatment goals are being individualized. Although the diagnostic thresholds for prediabetes and diabetes do not simply increase as a person gets older, blood sugar levels and treatment goals in older adults may need to be considered alongside overall health, functional status, other medical conditions, and the risk of hypoglycemia.
The diagnostic charts on this page are designed primarily for nonpregnant individuals.
Pregnancy and gestational diabetes use different testing approaches and glucose targets. If you are pregnant, follow the ranges provided by your obstetric and diabetes care team rather than applying the nonpregnancy chart to yourself.
Blood sugar charts are useful because they put a lot of information in one place. They can also create unnecessary worry when different types of glucose measurements are mixed together.
The most common example I see is someone comparing a glucose reading after an ordinary meal with the two-hour value from an oral glucose tolerance test. They may both be called “two-hour glucose,” but they are not the same test.
I also try to separate diagnostic thresholds from treatment targets. A person who does not have a diabetes diagnosis and a person who is already being treated for diabetes should not use the same table for the same purpose.
Use the chart to understand your numbers, but use repeated patterns, symptoms, laboratory testing and your individual medical situation to decide what those numbers actually mean for you.
— Dr. Albana Greca
For a nonpregnant adult being evaluated for diabetes, a laboratory fasting plasma glucose of 99 mg/dL or below is within the normal diagnostic range.
A properly performed fasting laboratory plasma glucose of 100 mg/dL falls at the beginning of the prediabetes range of 100–125 mg/dL.
A single result does not necessarily establish a diagnosis. Your doctor may consider repeat testing, HbA1c or another appropriate test.
It depends on what test you mean.
During a standardized 75-g OGTT, a two-hour value of 140 mg/dL is within the impaired glucose tolerance range.
A glucose reading of 140 mg/dL two hours after an ordinary meal is different. It should not automatically be labeled prediabetes using the OGTT chart.
Yes. Fasting plasma glucose, HbA1c and the two-hour 75-g OGTT measure different aspects of glucose metabolism and do not always identify exactly the same people.
A person may have fasting glucose below the diabetes threshold but have another appropriate laboratory test in the diabetes range. This is why diabetes should not be diagnosed from one ordinary after-meal home reading.
For people with diabetes, glucose below 70 mg/dL is the hypoglycemia alert threshold. A result below 54 mg/dL represents level 2 hypoglycemia and requires immediate action.
No. Home meters are designed for glucose monitoring. If repeated readings concern you, discuss laboratory testing with your healthcare professional.
The safest way to use a blood sugar chart is to first identify what kind of number you have.
A chart gives you the numbers. Your test type, timing, symptoms, repeated pattern and individual health situation tell you what those numbers mean.
Medical disclaimer: This page provides general medical education and is not a substitute for individualized diagnosis, treatment or emergency care. Do not start, stop or change insulin or another diabetes medicine solely on the basis of an online chart.