Normal fasting blood sugar is 99 mg/dL or below. Levels between 100 and 125 mg/dL fall into the prediabetes range, and 126 mg/dL or higher indicates diabetes. These numbers shift depending on when you last ate, your age, whether you’re pregnant, and how the test is performed.
Fasting Blood Sugar Ranges
A fasting blood sugar test measures glucose after you haven’t eaten for at least eight hours, usually first thing in the morning. It’s the most common screening tool and the one your doctor will likely order first.
- Normal: 99 mg/dL or below
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or above
A single high reading doesn’t automatically mean diabetes. The test is typically repeated on a separate day to confirm. If your fasting number lands in the prediabetes zone, it means your body is starting to struggle with processing glucose but hasn’t crossed the threshold into diabetes yet.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal as your body breaks down carbohydrates into glucose. In someone without diabetes, levels peak about one to two hours after eating and then return to baseline. The standard benchmark is a two-hour postprandial (after-meal) reading.
- Without diabetes: below 140 mg/dL at two hours
- With diabetes: below 180 mg/dL at two hours is the typical target
If you’re managing diabetes, that 180 mg/dL target gives your body more room while still keeping glucose in a zone that reduces long-term complications. Consistently exceeding it after meals is a sign that medication, meal timing, or carbohydrate intake may need adjusting.
The A1C Test
While a fasting test captures a single moment, the A1C test reflects your average blood sugar over the past two to three months. It measures the percentage of hemoglobin (a protein in red blood cells) that has glucose attached to it. The higher your blood sugar has been running, the higher the percentage.
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
A1C is useful because it isn’t thrown off by what you ate yesterday or how well you slept. It shows the bigger picture. For people already diagnosed with diabetes, most guidelines suggest keeping A1C below 7%, though your target may be different depending on age and overall health.
The Glucose Tolerance Test
This test is used when fasting numbers are borderline or when screening during pregnancy. You drink a sugary solution and then have your blood drawn at timed intervals to see how efficiently your body clears glucose.
For a standard two-hour oral glucose tolerance test:
- Normal: 140 mg/dL or below at two hours
- Prediabetes: 140 to 199 mg/dL
- Diabetes: 200 mg/dL or above
A random blood sugar test, taken at any time regardless of meals, can also flag diabetes if the result is 200 mg/dL or above and you’re experiencing symptoms like excessive thirst or frequent urination.
Blood Sugar Targets During Pregnancy
Pregnancy changes how your body handles insulin, and gestational diabetes develops in a significant number of pregnancies. The thresholds are stricter than standard diabetes screening because even moderately elevated glucose can affect fetal development.
Most pregnant people take a one-hour glucose challenge first. A result of 190 mg/dL or higher at the one-hour mark points to gestational diabetes. If the result is elevated but below that cutoff, a follow-up three-hour test is used with these benchmarks:
- Fasting: 95 mg/dL or lower
- One hour: 180 mg/dL or lower
- Two hours: 155 mg/dL or lower
- Three hours: 140 mg/dL or lower
Exceeding the cutoff at two or more of these time points results in a gestational diabetes diagnosis. Some providers use a standalone two-hour test instead, with slightly different numbers: a fasting level of 92 mg/dL or higher, 180 mg/dL or higher at one hour, or 153 mg/dL or higher at two hours.
Targets for Children
Children with type 1 diabetes have age-adjusted targets that account for the fact that young kids are more vulnerable to the effects of low blood sugar and less able to recognize or communicate symptoms.
- Under 5 years: 80 to 200 mg/dL
- Ages 5 to 11: 70 to 180 mg/dL
- 12 and older: 70 to 150 mg/dL
The wider range for younger children is intentional. A toddler who drops too low may not be able to tell a parent they feel shaky or confused, so the safety margin is larger.
Targets for Older Adults
Tight blood sugar control becomes riskier as people age. Older adults who have memory problems, vision issues, kidney disease, or a history of severe low blood sugar episodes are more likely to experience dangerous drops if targets are set too aggressively. For these individuals, the goal shifts from hitting textbook numbers to achieving the best control possible without triggering hypoglycemia. That often means accepting A1C levels somewhat above 7% in exchange for fewer dangerous lows.
When Blood Sugar Drops Too Low
Hypoglycemia, or low blood sugar, is categorized in three levels based on severity:
- Level 1: 54 to 69 mg/dL. You may feel shaky, sweaty, or hungry. This can usually be corrected by eating fast-acting carbohydrates like juice or glucose tablets.
- Level 2: below 54 mg/dL. Symptoms become more serious and can include confusion, blurred vision, and difficulty speaking. This requires immediate treatment.
- Level 3: a severe event where you need someone else’s help to recover, regardless of the number on the meter. This can involve seizures or loss of consciousness.
Hypoglycemia is most common in people taking insulin or certain oral diabetes medications. It’s uncommon in people without diabetes, though it can happen after prolonged fasting or intense exercise.
What Affects Your Numbers
Blood sugar isn’t static. It fluctuates throughout the day in response to a range of factors beyond food. Stress is one of the most significant. When your body perceives a threat, it triggers a cascade: insulin levels drop, adrenaline rises, and the liver releases stored glucose to fuel a fight-or-flight response. At the same time, cortisol and growth hormone make your muscles and fat tissue less responsive to insulin. The result is more glucose floating in your bloodstream with less ability to clear it. For someone with diabetes, a stressful day can push readings noticeably higher even without any change in diet.
Sleep also plays a role. Poor or insufficient sleep reduces insulin sensitivity, meaning your cells don’t absorb glucose as effectively. Illness and infection raise blood sugar because the immune response triggers many of the same stress hormones. Even the time of day matters: many people experience a “dawn phenomenon” where blood sugar rises in the early morning hours due to a natural surge in hormones that prepare the body to wake up.
Continuous Glucose Monitors and Time in Range
Continuous glucose monitors (CGMs) are small sensors worn on the body that check glucose every few minutes, giving a much more complete picture than occasional finger sticks. One of the most useful metrics they provide is “time in range,” which measures the percentage of the day your blood sugar stays between 70 and 180 mg/dL.
The target for most people with diabetes is spending at least 70% of the day in range, roughly 17 out of 24 hours. This metric has become increasingly important because it captures not just the highs and lows but the overall stability of your glucose throughout the day. Two people can have the same A1C but very different day-to-day patterns: one with steady levels and another swinging between spikes and crashes. Time in range reveals that difference in a way A1C alone cannot.