Blood Sugar Level Chart: Normal Ranges and Diabetes Risk

Blood sugar (also called blood glucose) is one of the most useful health numbers to understand. The thresholds below come from the American Diabetes Association diagnostic guidelines and are widely used internationally. They are based on standard laboratory measurements, not on home glucose meter readings, which can vary by 10–15 percent.

Blood Sugar Categories

Fasting Blood Sugar

Measured after at least 8 hours without eating, typically first thing in the morning.

Category	mg/dL	mmol/L
Normal	Less than 100	Less than 5.6
Prediabetes	100 to 125	5.6 to 6.9
Diabetes	126 or higher	7.0 or higher

2-Hour Post-Meal Blood Sugar

Measured 2 hours after the start of a meal, or as part of an oral glucose tolerance test.

Category	mg/dL	mmol/L
Normal	Less than 140	Less than 7.8
Prediabetes	140 to 199	7.8 to 11.0
Diabetes	200 or higher	11.1 or higher

HbA1c (Average Over 2-3 Months)

The HbA1c, or A1C, test reflects average blood sugar over the previous 2 to 3 months. It does not require fasting.

Category	HbA1c (%)	Average glucose (mg/dL)
Normal	Below 5.7	Below 117
Prediabetes	5.7 to 6.4	117 to 137
Diabetes	6.5 or higher	140 or higher

A Note on the Different Tests

A diabetes diagnosis usually requires either two abnormal readings on different days, or an abnormal reading along with classic symptoms (excessive thirst, frequent urination, fatigue, unexplained weight loss). A single high reading is not enough on its own, since blood sugar can spike for various reasons including stress, illness, or even a particularly carb-heavy meal the day before a fasting test.

Why Prediabetes Matters

Prediabetes is not a mild form of diabetes — it is a stage where blood sugar is elevated but not yet at diabetes levels. Without intervention, many people with prediabetes progress to type 2 diabetes within several years. The good news is that lifestyle changes (weight loss, regular activity, dietary improvements) reduce the risk of progression substantially. The Diabetes Prevention Program demonstrated a 58 percent reduction in progression to diabetes through lifestyle changes alone.

According to the CDC, more than one in three US adults has prediabetes, and most do not know it. Asking your doctor for a simple blood test can be one of the most useful things you do for your long-term health.

Symptoms of High Blood Sugar

• Excessive thirst
• Frequent urination, particularly at night
• Fatigue
• Blurred vision
• Slow-healing cuts and bruises
• Unexplained weight loss (more common in type 1 diabetes)
• Frequent infections

Symptoms often develop slowly with type 2 diabetes, which is why screening matters. Type 1 diabetes can develop more quickly, particularly in children and young adults, and can become a medical emergency — watch for nausea, fruity-smelling breath, rapid breathing, or confusion.

Symptoms of Low Blood Sugar

Hypoglycemia (blood sugar below 70 mg/dL) is most common in people taking insulin or certain diabetes medications, but can occur in others. Signs include shakiness, sweating, hunger, dizziness, and confusion. If you have diabetes and use insulin, your healthcare team will give you specific guidance on how to recognize and treat low blood sugar.

When to Get Tested

The American Diabetes Association recommends screening:

• All adults starting at age 35.
• Earlier and more frequently for people with risk factors: family history of diabetes, BMI of 25 or above, physical inactivity, certain ethnicities (including South Asian, African, Hispanic, Native American, and Pacific Islander), history of gestational diabetes, or PCOS.
• Annually for people with prediabetes.

Try Our Free Tools

• Blood Sugar Checker — enter a reading and see which category it falls in.
• Diabetes Risk Assessment — estimate your risk and see what factors apply.
• BMI Calculator — weight is one of the strongest modifiable risk factors.

Sources and Further Reading

• American Diabetes Association. Diagnosis.
• Centers for Disease Control and Prevention. Getting Tested for Diabetes.
• National Institute of Diabetes and Digestive and Kidney Diseases. Tests and Diagnosis.

Blood Sugar Conversions: mg/dL and mmol/L

Different countries report blood glucose using different units. The United States uses milligrams per deciliter (mg/dL); most of the world uses millimoles per liter (mmol/L). To convert, divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL.

• 70 mg/dL = 3.9 mmol/L (lower edge of normal fasting)
• 100 mg/dL = 5.6 mmol/L (upper edge of normal fasting)
• 126 mg/dL = 7.0 mmol/L (diabetes diagnostic threshold for fasting)
• 140 mg/dL = 7.8 mmol/L (upper edge of normal post-meal)
• 200 mg/dL = 11.1 mmol/L (diabetes threshold for post-meal or random)

A1C and Estimated Average Glucose

Hemoglobin A1C reflects average blood glucose over the prior 2 to 3 months. It is the gold standard for assessing long-term blood sugar control. Approximate equivalents:

• 5.0% A1C = average glucose 97 mg/dL (5.4 mmol/L)
• 5.7% A1C = average 117 mg/dL (6.5 mmol/L) - upper edge of normal
• 6.0% A1C = average 126 mg/dL (7.0 mmol/L)
• 6.5% A1C = average 140 mg/dL (7.8 mmol/L) - diabetes diagnostic threshold
• 7.0% A1C = average 154 mg/dL (8.6 mmol/L) - typical target for people with diabetes
• 8.0% A1C = average 183 mg/dL (10.2 mmol/L)
• 9.0% A1C = average 212 mg/dL (11.8 mmol/L)

Why Home Glucose Readings Vary

If your home meter readings seem inconsistent, that's normal. Several factors can affect a single reading:

• Recent food or drink. Even sugar-free gum or coffee can shift readings.
• Stress, illness, or pain. Each can raise blood glucose by 20 to 50 mg/dL or more.
• Time since last meal. Glucose is constantly changing in response to food and insulin.
• Hand cleanliness. Sugar residue (from fruit, juice, food prep) on fingers gives falsely high readings.
• Strip and meter accuracy. Most meters are within 15 percent of lab values; old strips or extreme temperatures reduce accuracy.
• Hydration. Dehydration can artificially raise readings.
• Medications. Steroids, certain blood pressure medications, and others affect glucose.
• Hormonal cycles. Menstrual cycle and pregnancy affect insulin sensitivity.

What Counts as a Diabetes Diagnosis?

According to the American Diabetes Association, a diabetes diagnosis requires any one of the following, confirmed on a separate day:

• Fasting glucose 126 mg/dL (7.0 mmol/L) or higher
• Random glucose 200 mg/dL (11.1 mmol/L) or higher with classic symptoms
• 2-hour glucose 200 mg/dL or higher during an oral glucose tolerance test
• HbA1c 6.5 percent or higher

One abnormal reading is not a diagnosis. The same test must be repeated on a different day, or another type of test must confirm.

Recognizing Hypoglycemia (Low Blood Sugar)

Blood sugar below 70 mg/dL (3.9 mmol/L) is considered low. This is most relevant for people taking insulin or sulfonylurea medications. Symptoms include:

• Shakiness, sweating, and fast heartbeat
• Hunger
• Confusion or difficulty concentrating
• Irritability or anxiety
• Pale skin
• Dizziness or weakness
• Severe lows: seizures, loss of consciousness

If you have diabetes and experience symptoms of low blood sugar, follow the "15-15 rule": consume 15 grams of fast-acting carbs (4 oz juice, glucose tablets, or hard candy), wait 15 minutes, and recheck.

When to Talk to Your Doctor

• Repeated readings in the prediabetes or diabetes range
• Classic symptoms: excessive thirst, frequent urination, unexplained weight loss, blurred vision
• A reading above 240 mg/dL (13.3 mmol/L) with symptoms (call your doctor that day)
• Reading above 300 mg/dL (16.7 mmol/L) with nausea, vomiting, abdominal pain, or confusion (seek emergency care)
• Frequent low readings, especially if you take diabetes medication
• If you have not been screened and have risk factors (overweight, family history, age 35+, certain ethnic backgrounds)

Try Our Free Tools

Quickly check where a single reading falls with our Free Blood Sugar Checker, or estimate your overall risk with our Diabetes Risk Assessment & A1C Converter. For lifestyle approaches that reduce blood sugar, see 10 Ways to Lower Blood Sugar Naturally.

Frequently Asked Questions

Why does my fasting reading vary so much?

The dawn phenomenon causes natural early-morning rises in blood glucose. Stress, sleep quality, what you ate the previous evening, and other factors also play a role. Trends over weeks matter more than single readings.

Can stress alone raise blood sugar?

Yes. Acute stress triggers cortisol and adrenaline release, both of which raise blood glucose. Chronic stress contributes to ongoing insulin resistance.

How often should I check if I am not diabetic?

Routine home glucose checks are not necessary for most non-diabetic adults. The ADA recommends a fasting glucose or A1C check at least every 3 years starting at age 35, more often with risk factors.

Can lifestyle changes reverse prediabetes?

Often yes. The Diabetes Prevention Program studies showed lifestyle changes prevented or delayed progression to type 2 diabetes in over half of high-risk participants.

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