A healthy fasting glucose level is 99 mg/dL or below, and a reading two hours after eating should stay under 140 mg/dL. Those two numbers give most people a reliable picture of where they stand. But glucose targets shift depending on whether you’re fasting, just finished a meal, managing diabetes, or older with other health concerns. Here’s what each number means and how to interpret yours.
Fasting Blood Sugar Targets
A fasting blood sugar test measures your glucose after at least eight hours without food, typically first thing in the morning. For a healthy adult without diabetes, normal is 99 mg/dL or below. Once you cross into the 100 to 125 mg/dL range, that’s considered prediabetes. A fasting reading of 126 mg/dL or higher on two separate tests meets the diagnostic threshold for type 2 diabetes.
Prediabetes is worth paying attention to because it doesn’t cause obvious symptoms. Roughly 1 in 3 American adults falls into that 100 to 125 mg/dL window without knowing it. The good news is that prediabetes is reversible with changes to diet, activity, and weight. A single high fasting reading doesn’t automatically mean trouble, but a pattern of readings above 100 mg/dL warrants a closer look.
After-Meal Glucose Levels
Your blood sugar naturally rises after you eat, then gradually comes back down as your body processes the glucose. A test taken two hours after a meal should show a reading below 140 mg/dL if you don’t have diabetes. If you do have diabetes, the target is below 180 mg/dL two hours after eating.
A two-hour post-meal reading between 140 and 199 mg/dL (in someone not previously diagnosed) falls into the prediabetes range. A result of 200 mg/dL or higher points toward diabetes. These post-meal numbers can sometimes catch blood sugar problems that a fasting test misses, which is why doctors occasionally use a glucose tolerance test where you drink a sugary solution and have your blood drawn two hours later.
What Your A1C Tells You
While fasting and post-meal tests capture a snapshot, the A1C test shows your average blood sugar over the past two to three months. It measures the percentage of your red blood cells that have glucose attached to them. A normal A1C is below 5.7%. Prediabetes falls between 5.7% and 6.4%. An A1C of 6.5% or higher indicates diabetes.
The A1C is useful because it smooths out day-to-day fluctuations. You might have a great fasting number one morning after sleeping well and eating lightly, but your three-month average could tell a different story. If your doctor orders only one glucose-related test during a routine checkup, it’s often this one.
Targets If You Have Diabetes
If you’ve already been diagnosed with diabetes, your targets are slightly different from the “normal” ranges used for screening. Most adults with type 1 or type 2 diabetes aim for a fasting glucose between 80 and 130 mg/dL and a post-meal reading below 180 mg/dL. The A1C goal for most people with diabetes is below 7%, though your doctor may set a more or less aggressive target based on your situation.
For people using a continuous glucose monitor (a small sensor worn on the skin that tracks glucose around the clock), the key metric is “time in range,” meaning the percentage of the day your glucose stays between 70 and 180 mg/dL. The international consensus recommendation is to spend more than 70% of the day in that window, which works out to roughly 17 hours. Older adults or those at higher risk for low blood sugar may aim for at least 50% time in range instead.
How Targets Change With Age
Older adults face a tricky balancing act. Low blood sugar (hypoglycemia) becomes more dangerous with age because it increases the risk of falls, confusion, and heart problems. Irregular eating patterns, declining kidney function, and multiple medications all make blood sugar harder to predict.
For healthy older adults with few other medical conditions, the recommended A1C goal is below 7.0% to 7.5%. For those with multiple chronic conditions or cognitive decline, the target loosens to below 8.0%. And for older adults in poor health, the priority shifts away from hitting a specific number and toward simply avoiding dangerous lows and symptomatic highs. This is why a 75-year-old with heart disease and a 35-year-old with new-onset type 2 diabetes won’t have the same glucose targets, even though they share a diagnosis.
When High Blood Sugar Causes Symptoms
One reason glucose problems go undetected is that high blood sugar typically doesn’t produce noticeable symptoms until levels climb above 180 to 200 mg/dL. At that point you might experience increased thirst, frequent urination, blurred vision, fatigue, or headaches. Someone with prediabetes at 115 mg/dL fasting will feel perfectly fine, which is exactly why routine testing matters.
On the low end, symptoms of hypoglycemia (shakiness, sweating, confusion, irritability) usually appear when glucose drops below about 70 mg/dL. This is primarily a concern for people taking insulin or certain diabetes medications rather than for the general population.
What Can Throw Off a Reading
If you’re testing at home with a fingerstick meter, several factors can skew your results. Dehydration tends to concentrate glucose in the blood, producing a falsely high number. Anemia (a low red blood cell count) can also reduce accuracy. Dirt, lotion, or alcohol residue on your fingertip may interfere with the test strip, so washing your hands with soap and water before testing gives you the most reliable reading.
Extreme temperatures affect test strips too. If your meter has been sitting in a hot car or freezing garage, the reading may not be trustworthy. Stress, illness, and poor sleep can all temporarily raise blood sugar even if your diet hasn’t changed. A single unusual number isn’t necessarily a sign of a problem. Patterns over days and weeks matter far more than any individual reading.
Quick Reference: Glucose Ranges
- Fasting (no food for 8+ hours): Normal is 99 mg/dL or below; prediabetes is 100 to 125 mg/dL; diabetes is 126 mg/dL or higher
- Two hours after eating: Normal is below 140 mg/dL; prediabetes is 140 to 199 mg/dL; diabetes is 200 mg/dL or higher
- A1C: Normal is below 5.7%; prediabetes is 5.7% to 6.4%; diabetes is 6.5% or higher
- Random blood sugar: A reading of 200 mg/dL or higher at any time, combined with symptoms, suggests diabetes