A normal fasting blood sugar level is below 100 mg/dL (5.6 mmol/L), measured after at least eight hours without eating. That single number is the most common benchmark, but “normal” looks different depending on when you last ate, whether you’re pregnant, and how the measurement is taken. Here’s what each number means and why it matters.
Fasting Blood Sugar Ranges
Fasting glucose is the standard starting point for evaluating blood sugar. It’s typically drawn first thing in the morning before breakfast. The thresholds break down cleanly into three categories:
- Normal: below 100 mg/dL (5.6 mmol/L)
- Prediabetes: 100 to 125 mg/dL (5.6 to 6.9 mmol/L)
- Diabetes: 126 mg/dL (7.0 mmol/L) or higher on two separate tests
That two-test requirement for a diabetes diagnosis is important. A single high reading can reflect stress, illness, or a lab error. Two elevated results on different days confirm a pattern rather than a fluke.
Blood Sugar After Eating
Your blood sugar naturally rises after a meal, peaking somewhere around 30 to 60 minutes after you start eating. In a person without diabetes, it typically returns close to baseline within two to three hours. For most healthy adults, blood sugar after a meal stays below 140 mg/dL.
For people managing diabetes, the clinical target is a bit more generous. The American Diabetes Association’s 2025 guidelines recommend a peak post-meal reading below 180 mg/dL and a pre-meal range of 80 to 130 mg/dL. These wider targets reflect the reality that tightly controlling blood sugar with medication carries its own risks, particularly dangerously low readings.
A1C: Your Three-Month Average
While fasting glucose captures a single moment, the A1C test reflects your average blood sugar over roughly two to three months. It measures the percentage of hemoglobin (a protein in red blood cells) that has glucose attached to it. The more sugar in your blood over time, the higher the percentage.
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or above
A1C is especially useful because it isn’t thrown off by what you ate the night before or how stressed you felt that morning. It gives a broader picture. For people already diagnosed with diabetes, the 2025 guidelines recommend keeping A1C below 7% in most cases, though older adults or people prone to low blood sugar episodes may have a more relaxed target.
What Continuous Glucose Monitors Reveal
Continuous glucose monitors (CGMs) have given researchers a much clearer picture of what blood sugar actually does throughout the day in healthy people. A large community-based study of people without diabetes found that their average glucose was about 114.5 mg/dL. They spent roughly 98% of the day between 70 and 180 mg/dL, and about 87% of the day in the tighter 70 to 140 mg/dL range.
Even in these healthy participants, blood sugar spiked above 180 mg/dL for more than 15 minutes per day on average. That’s a reassuring detail: brief spikes after a meal are normal, not a sign of disease. What matters is how quickly levels come back down and where they spend most of their time. If you wear a CGM out of curiosity or for general wellness tracking, spending 70% or more of your time between 70 and 180 mg/dL is the benchmark clinicians use for good glucose control.
Ranges for Children and Older Adults
Children, especially young ones, have slightly wider target ranges. For kids under 5, a blood sugar between 80 and 200 mg/dL is considered a reasonable goal. Children aged 5 to 11 have a target of 70 to 180 mg/dL, and by age 12 and up, the goal narrows to 70 to 150 mg/dL. These pediatric ranges are broader because young children are more vulnerable to the effects of low blood sugar and less able to recognize or communicate symptoms.
Older adults also get some flexibility. The 2025 guidelines suggest that older people using a CGM aim for at least 50% of the day in the 70 to 180 mg/dL range (compared to 70% for younger adults) and spend no more than 15 minutes per day below 70 mg/dL. Low blood sugar in older adults raises the risk of falls, confusion, and cardiac events, so the priority shifts toward avoiding dangerous lows rather than keeping numbers as tight as possible.
Blood Sugar During Pregnancy
Pregnancy brings its own set of glucose thresholds. Gestational diabetes screening typically happens between 24 and 28 weeks using an oral glucose challenge: you drink a sugary solution, and your blood is drawn an hour later. A result at or above 140 mg/dL usually triggers a longer, more detailed follow-up test. For screening with a simple fasting blood draw at 24 weeks or later, values at or below 80 mg/dL are generally low enough to rule out gestational diabetes, while readings at 90 mg/dL or above warrant closer evaluation.
Why Morning Readings Can Run High
If you’ve noticed your fasting blood sugar is higher than expected, you’re not imagining it. The most common explanation is the dawn phenomenon. In the early morning hours, your body releases cortisol and growth hormone, both of which signal the liver to produce more glucose. This is your body’s natural alarm clock, giving you energy to start the day. In someone without diabetes, insulin rises in response and keeps blood sugar in check. In someone with diabetes or insulin resistance, that compensating insulin response falls short, and morning readings climb.
A less common cause is the Somogyi effect: your blood sugar drops too low overnight (from too much insulin or a skipped meal), and your liver overcompensates by dumping glucose into your bloodstream. The result looks the same on a morning reading, a high number, but the cause is the opposite. The simplest way to tell the difference is to check your blood sugar at bedtime and again around 2 or 3 a.m. If you’re low in the middle of the night and high in the morning, the Somogyi effect is likely. If you’re normal at bedtime and steadily rise, it’s the dawn phenomenon.
How Your Body Keeps Sugar in Range
Blood sugar regulation is a constant balancing act between hormones that lower glucose and hormones that raise it. Insulin, produced by beta cells in the pancreas, is the primary hormone that brings sugar levels down. It acts like a key, unlocking cells so they can absorb glucose from the bloodstream for energy or storage.
On the other side, glucagon (also made in the pancreas, by alpha cells) tells the liver to release stored glucose when levels drop too low. Your liver acts as a fuel reservoir, storing glucose when there’s plenty and releasing it between meals and overnight. Several other hormones push blood sugar upward too: adrenaline during stress or exercise, cortisol from the adrenal glands, and growth hormone from the brain. These are sometimes called counter-regulatory hormones because they work against insulin’s glucose-lowering effect.
Your gut also plays a role. When food arrives in the intestine, it triggers hormones called incretins that amplify insulin release and dial down glucagon at the same time. This is why eating a meal produces a more robust insulin response than injecting the same amount of glucose directly into the bloodstream. When any piece of this system weakens, whether the pancreas makes less insulin, the liver overproduces glucose, or cells stop responding to insulin efficiently, blood sugar starts drifting out of its normal range.
What Low Blood Sugar Feels Like
Normal blood sugar has a floor, not just a ceiling. Below 70 mg/dL is considered mild low blood sugar, and you might feel shaky, sweaty, irritable, or suddenly hungry. Below 54 mg/dL is where the brain starts losing its primary fuel source, and symptoms can escalate to confusion, blurred vision, difficulty speaking, or loss of coordination. Severe low blood sugar, where you need someone else’s help to recover, can happen at any reading and is a medical emergency.
Low blood sugar is most common in people taking insulin or certain diabetes medications, but it can occasionally happen in people without diabetes after prolonged fasting, intense exercise, or heavy alcohol consumption.