What Is a Normal Blood Sugar Level? US Ranges Explained

The Two Blood Sugar Tests on Your Report

Your blood test report likely includes one or both of these glucose measurements:

Fasting glucose is measured after at least 8 hours without eating. It's the standard test for diabetes screening included in most Comprehensive Metabolic Panels (CMP). It reflects your baseline blood sugar when your body is in a fasted state.

HbA1c (Hemoglobin A1c) reflects your average blood sugar over the past 2–3 months. It's not affected by what you ate the day before the test, making it a more stable long-term indicator. Most doctors now use HbA1c as the primary diagnostic tool for diabetes.

US Blood Sugar Ranges — The Official Guidelines

These ranges come from the American Diabetes Association (ADA), which sets the standard used by US labs including Quest Diagnostics and LabCorp:

Category	Fasting Glucose	HbA1c
Normal	70–99 mg/dL	Below 5.7%
Pre-diabetes	100–125 mg/dL	5.7–6.4%
Diabetes	126 mg/dL or above	6.5% or above
Optimal (research-based)	70–85 mg/dL	4.8–5.4%

Note the difference between "normal" and "optimal." A fasting glucose of 98 mg/dL is technically normal by US lab standards — but it is very close to the pre-diabetes threshold. Many longevity researchers consider 70–85 mg/dL to be the optimal range for minimising long-term metabolic risk.

Pre-Diabetes: The Range Most People Don't Take Seriously Enough

Approximately 96 million American adults — more than 1 in 3 — have pre-diabetes. Critically, around 80% of them don't know it. Pre-diabetes causes no symptoms; the only way to detect it is through a blood test.

Pre-diabetes matters because it is highly reversible. Research from the CDC's National Diabetes Prevention Program shows that people with pre-diabetes who make moderate lifestyle changes — losing 5–7% of body weight and doing 150 minutes of moderate physical activity per week — reduce their risk of developing type 2 diabetes by 58%. In adults over 60, the reduction is 71%.

If your fasting glucose is between 100–125 mg/dL, this is a meaningful signal worth acting on — not just monitoring.

What Affects Your Fasting Glucose Result

Fasting glucose is more variable than most people realize. A single reading can be affected by how well you slept the night before (poor sleep raises cortisol, which raises blood sugar), physical or emotional stress around the time of the test, illness, certain medications including steroids and some antidepressants, and how long you actually fasted before the draw.

This is one reason HbA1c is often more reliable for diagnosis — it averages out day-to-day fluctuations. If your fasting glucose is borderline high on one test, your doctor will usually confirm with a repeat test or add HbA1c before making a diagnosis.

What Optimal Blood Sugar Actually Looks Like

Research on long-lived, metabolically healthy populations consistently shows fasting glucose in the 70–85 mg/dL range and HbA1c between 4.8–5.2%. These aren't dangerous low values — they represent the body efficiently processing glucose with good insulin sensitivity.

For people without a diabetes diagnosis, the lifestyle pathway to improving blood sugar typically involves reducing refined carbohydrates and added sugar, increasing fibre intake, consistent physical activity (particularly resistance training and walking after meals), and maintaining a healthy body weight. If you have been diagnosed with diabetes or pre-diabetes, always follow your doctor's guidance — lifestyle changes and medication are often used together, not in place of each other.

When to Talk to Your Doctor

Contact your doctor if your fasting glucose is 100 mg/dL or above on a confirmed test, if your HbA1c is 5.7% or above, if you have symptoms of high blood sugar (frequent urination, excessive thirst, fatigue, blurred vision), or if you have risk factors for diabetes — family history, obesity, previous gestational diabetes, or PCOS.