A good fasting blood glucose level is below 100 mg/dL (5.6 mmol/L). After eating, a healthy reading stays below 140 mg/dL when checked two hours after a meal. These two numbers give you the clearest snapshot of how well your body manages sugar, but the full picture depends on when you test, your age, and whether you’re pregnant or managing diabetes.
Fasting Blood Glucose: The Baseline Number
Fasting blood glucose is measured after you haven’t eaten for at least eight hours, typically first thing in the morning. It reflects how well your body regulates sugar on its own, without the influence of a recent meal. The standard categories break down like this:
- Normal: below 100 mg/dL
- Prediabetes: 100 to 125 mg/dL
- Diabetes: 126 mg/dL or higher
A single high reading doesn’t automatically mean you have diabetes. Doctors typically confirm with a repeat test on a different day. But if your fasting numbers consistently land in the 100 to 125 range, your body is already struggling to process sugar efficiently, even if you feel fine.
After-Meal Blood Glucose
Your blood sugar naturally rises after you eat. In a healthy body, insulin brings it back down within a couple of hours. When tested two hours after a meal, a normal reading falls between 70 and 140 mg/dL. Prediabetic levels range from 141 to 200 mg/dL, and anything above 200 mg/dL points toward diabetes.
If you’re already managing diabetes, the targets are slightly more relaxed. The general goal is to stay below 180 mg/dL two hours after eating and below 130 mg/dL when fasting. These wider ranges reflect the reality that tightly controlling blood sugar with medication carries its own risks, particularly dangerous lows.
What A1C Tells You That a Single Test Can’t
A single finger-stick reading is a snapshot of one moment. Your A1C (also called HbA1c) reflects your average blood sugar over the previous two to three months. It works by measuring how much sugar has attached to your red blood cells, which live for roughly that long.
- Normal: below 5.7%
- Prediabetes: 5.7% to 6.4%
- Diabetes: 6.5% or higher
Each percentage point corresponds to a daily average. An A1C of 5% translates to an average blood sugar of about 97 mg/dL. At 6%, it’s roughly 126 mg/dL. At 7%, which is a common treatment target for people with diabetes, the average sits around 154 mg/dL. The relationship is fairly linear: each 1% increase in A1C adds about 28 to 29 mg/dL to your estimated average.
A1C is useful because it smooths out the daily ups and downs. You could have a perfect fasting number on the morning of your lab work but still have an elevated A1C if your blood sugar spikes significantly after meals or runs high overnight.
Targets During Pregnancy
Pregnancy changes how the body handles sugar. Hormones produced by the placenta can make cells more resistant to insulin, so the thresholds for concern are tighter than they are for the general population.
Most pregnant women undergo a glucose screening between weeks 24 and 28. In the initial one-hour screening test, a result of 190 mg/dL or higher indicates gestational diabetes. If the first test is borderline, a longer three-hour follow-up is used, with these cutoffs:
- Fasting: 95 mg/dL or lower is expected
- One hour after glucose drink: 180 mg/dL or lower
- Two hours: 155 mg/dL or lower
- Three hours: 140 mg/dL or lower
Notice that the fasting target for pregnancy (95 mg/dL) is stricter than the general threshold of 100 mg/dL. That’s because even mildly elevated sugar during pregnancy can affect fetal growth and delivery outcomes.
How Targets Shift With Age
For older adults, especially those with multiple health conditions, the standard targets often get loosened. Pushing blood sugar very low with aggressive treatment (aiming for an A1C below 6.5%) has been associated with increased risk of dangerous lows, cardiovascular events, and falls. For someone in their 70s or 80s with other significant health concerns, a doctor may set a higher A1C target to balance blood sugar control against these risks.
The appropriate target depends on a long list of individual factors: how long someone has had diabetes, their cognitive function, whether they live independently, their history of low blood sugar episodes, and their overall life expectancy. There is no single “right” number for every older adult, which is why individualized targets matter more with age.
Time in Range: A Newer Way to Measure
If you use a continuous glucose monitor (CGM), the sensor on your arm or abdomen checks your sugar every few minutes and gives you a running picture rather than isolated snapshots. The key metric here is “time in range,” meaning the percentage of the day your glucose stays between 70 and 180 mg/dL. For most adults with Type 1 or Type 2 diabetes, the goal is to spend at least 70% of the day in that window.
Time in range captures something that fasting numbers and A1C can miss: variability. Two people can have the same A1C, but one might have steady blood sugar all day while the other swings between highs and lows. The person with more stable readings generally faces fewer complications over time, even if their average is the same.
Why Morning Readings Can Be Misleading
If you’ve ever checked your blood sugar first thing in the morning and found it surprisingly high despite not eating overnight, you’re not alone. There are a few common reasons this happens.
The most widespread is the dawn phenomenon. In the early morning hours, your body releases cortisol and growth hormone to prepare you for waking up. These hormones signal the liver to release stored sugar. In someone without diabetes, the pancreas responds with enough insulin to keep things balanced. If you have diabetes or insulin resistance, that compensating insulin response falls short, and you wake up with elevated readings.
A less common cause is called the Somogyi effect, which is essentially a rebound. If your blood sugar drops too low during the night, perhaps because of a skipped meal or too much evening insulin, your body overcompensates by dumping sugar into the bloodstream. The result is a high morning number that actually started as a low overnight. Checking your blood sugar at 2 or 3 a.m. for a few nights can help distinguish between these two patterns.
What the Numbers Mean in Practice
A fasting reading between 100 and 125 mg/dL places you in the prediabetes range, but that doesn’t make diabetes inevitable. Prediabetes is a signal that your body’s insulin system is under strain. Moderate changes to diet, physical activity, and weight (even a 5% to 7% loss in body weight) can bring numbers back into the normal range for many people.
If your fasting glucose is consistently below 100 mg/dL and your A1C is under 5.7%, your blood sugar regulation is working well. If either number is creeping upward, tracking your after-meal readings can reveal whether specific foods or meal sizes are pushing you higher than expected. Two-hour post-meal checks are the simplest way to see how your body responds to what you eat, and they’re more actionable than fasting numbers alone because they point directly to the meals and habits you can adjust.