Blood Sugar Levels Chart: Normal Ranges by Age and Time of Day
You prick your finger or glance at your CGM, see a number, and immediately wonder: is that good? Blood sugar targets shift depending on when you last ate, your age, whether you are pregnant, and whether you have diabetes at all. This guide lays out the standard reference ranges in one place — in both mg/dL and mmol/L — so you know exactly what your numbers mean.
What Blood Sugar Numbers Actually Mean
Blood glucose is measured as a concentration: how much sugar is dissolved in your blood at a given moment. In the United States, that concentration is expressed in milligrams per deciliter (mg/dL). Most of the rest of the world — including the UK, Canada, and Australia — uses millimoles per liter (mmol/L). The two describe the same thing on different scales, the way Fahrenheit and Celsius both describe temperature.
Converting between them is simple: divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to go the other way. A reading of 126 mg/dL is 7.0 mmol/L. A reading of 5.5 mmol/L is 99 mg/dL.
The other thing to understand is that glucose is a moving target. It dips overnight while you fast, climbs after meals as carbohydrates are digested, and responds to exercise, stress, illness, and hormones. That is why a "normal" number depends heavily on when the reading was taken. A value that is perfectly fine two hours after dinner might be flagged as high if it showed up on a fasting lab draw. Every chart below is organized around that timing.
Quick conversion tip: If you ever swap between apps or devices that use different units, remember the two anchor points: 100 mg/dL ≈ 5.6 mmol/L and 180 mg/dL = 10.0 mmol/L. Those two landmarks make it easy to sanity-check any conversion in your head.
Blood Sugar Levels Chart: General Targets
The most widely used targets for people with diabetes come from the American Diabetes Association (ADA). They apply to most non-pregnant adults with Type 1 or Type 2 diabetes. Alongside them, the table includes the reference ranges typically seen in people without diabetes, so you can see how the two compare.
| Time of Day | With Diabetes (ADA Target) | Without Diabetes (Reference) |
|---|---|---|
| Fasting / before meals | 80–130 mg/dL (4.4–7.2 mmol/L) |
70–99 mg/dL (3.9–5.5 mmol/L) |
| 1–2 hours after meals | Below 180 mg/dL (below 10.0 mmol/L) |
Below 140 mg/dL (below 7.8 mmol/L) |
| Bedtime | Often 90–150 mg/dL (5.0–8.3 mmol/L), individualized |
70–99 mg/dL (3.9–5.5 mmol/L) |
A few notes on reading this chart. The "fasting" row assumes at least eight hours without food, which is why it also serves as the before-breakfast target. The post-meal row is timed from the start of the meal, not the last bite — glucose usually peaks about an hour in. And the bedtime row is the least standardized of the three: many clinicians like to see a modest buffer above the low end of range before sleep, especially for people on insulin, but the exact window is something to set with your care team.
Notice that the diabetes targets are deliberately wider than the non-diabetic reference ranges. That is not a lower standard of care — it is a safety calculation. Chasing perfectly "normal" numbers with insulin or other glucose-lowering medication increases the risk of hypoglycemia, and the evidence says the wider window delivers excellent long-term outcomes with far less danger of severe lows.
Targets for Special Populations
Two groups get their own, notably different targets: pregnant individuals, where tighter control protects the developing baby, and older adults or those with complex health conditions, where looser targets reduce the risk of dangerous lows.
| Population | Typical Targets |
|---|---|
| Pregnancy (gestational or pre-existing diabetes) | Fasting below 95 mg/dL (5.3 mmol/L); 1 hour post-meal below 140 mg/dL (7.8 mmol/L); 2 hours post-meal below 120 mg/dL (6.7 mmol/L) |
| Older adults / high hypoglycemia risk | Often relaxed, e.g. 90–150 mg/dL (5.0–8.3 mmol/L) before meals, or wider — set individually based on health status and hypo awareness |
Children and teens with diabetes also tend to have individualized targets that balance growth, hypoglycemia risk, and the practical realities of school and sports; pediatric endocrinologists usually set these family by family rather than from a single chart. In every one of these cases, the numbers above are starting points, not prescriptions. Your own targets should always come from your care team, who can weigh your medications, history of lows, and overall health in a way no generic chart can.
When Blood Sugar Readings Are Dangerous
Most out-of-range readings are not emergencies — they are information. But two thresholds deserve immediate attention.
Below 54 mg/dL (3.0 mmol/L)
This is what clinicians call clinically significant hypoglycemia. At this level your brain is being starved of fuel, and symptoms like shakiness, sweating, confusion, and blurred vision can escalate quickly to an inability to treat yourself. The standard response is the rule of 15: take 15 grams of fast-acting carbohydrate (juice, glucose tabs), wait 15 minutes, and recheck. If someone is too confused to swallow safely or loses consciousness, that is a job for emergency glucagon and a 911 call — not juice.
Above 250 mg/dL (13.9 mmol/L) with ketones
A single high reading after a big meal is not a crisis. But glucose that stays above 250 mg/dL — especially alongside moderate or large ketones — signals that your body may not have enough insulin on board and is starting to burn fat for fuel. That is the on-ramp to diabetic ketoacidosis (DKA), a life-threatening emergency. Warning signs include nausea, vomiting, deep or rapid breathing, fruity-smelling breath, and unusual drowsiness. If highs persist and ketones are present, check your sick-day plan and contact your care team promptly; if DKA symptoms appear, seek emergency care.
Worth setting up now: If you use a CGM, configure your urgent-low alert at 55 mg/dL and make sure it can override your phone's silent mode. Severe lows are most dangerous when they happen overnight, and an alarm you can sleep through is not an alarm.
Why Your Target Range Might Be Different
If your endocrinologist has given you numbers that do not match this article, trust your endocrinologist. Targets are individualized for good reasons:
- Hypoglycemia unawareness. If you no longer feel lows coming, your team may raise your floor to rebuild your warning symptoms.
- Medication type. Someone managing Type 2 diabetes with metformin alone has a very different low-risk profile than someone on multiple daily insulin injections.
- How long you have had diabetes. Newly diagnosed people with long life expectancy often aim tighter; decades-long complications math can shift the balance.
- Other conditions. Heart disease, kidney disease, and cognitive impairment all change the risk calculus of aggressive targets.
The chart, in other words, is a map of the terrain — not your specific route through it.
A Single Reading Never Tells the Whole Story
Here is the limitation of every chart in this article: a blood sugar reading is a snapshot. A 110 mg/dL could be a rock-steady 110 that has held all morning, or it could be a brief stop on a plunge from 220 toward a low. The number is identical; the situations are completely different.
That is why modern diabetes care has moved toward continuous metrics — above all Time in Range, the percentage of the day your glucose stays inside your target window. Instead of judging yourself on isolated snapshots, you look at the whole film. We have a full explainer on what Time in Range is and why it matters more than A1C, plus a practical guide on how to track your Time in Range whether you use a CGM or fingersticks.
This is also where an app earns its keep. SweetLife lets you set a custom target range that matches whatever numbers your care team has given you — the standard 70–180, a tighter pregnancy window, or a looser individualized range — and then tracks your Time in Range against your targets, right on the home screen. Logged readings and meals get context instead of judgment, which makes it far easier to spot the pattern behind an odd number.
The takeaway: learn the chart, then zoom out. Knowing that 80–130 mg/dL is the pre-meal target matters less than knowing what fraction of your day you spend in range and which meals, doses, or habits pull you out of it.
Frequently Asked Questions
What is a normal blood sugar level for adults?
For adults without diabetes, normal fasting glucose is roughly 70–99 mg/dL (3.9–5.5 mmol/L), and post-meal readings typically stay below 140 mg/dL (7.8 mmol/L). For most adults with diabetes, the ADA recommends targeting 80–130 mg/dL before meals and below 180 mg/dL after meals — though your own care team may set different numbers based on your situation.
What should blood sugar be right after eating?
Glucose naturally rises after a meal and usually peaks around the one-hour mark. The ADA target for most adults with diabetes is below 180 mg/dL (10.0 mmol/L) measured one to two hours after the start of the meal. People without diabetes generally stay under 140 mg/dL (7.8 mmol/L). A reading taken minutes after your last bite will often look alarming simply because the rise has not finished — timing matters as much as the number.
What blood sugar level is dangerous?
Below 54 mg/dL (3.0 mmol/L) is clinically significant hypoglycemia and needs fast-acting carbs immediately. Sustained readings above 250 mg/dL (13.9 mmol/L) with moderate or large ketones raise the risk of DKA, a medical emergency. Confusion, vomiting, fruity breath, or extreme drowsiness at either end of the scale means it is time for urgent medical help, not another recheck.
Are targets different in mmol/L countries?
No — the targets are identical, only the units change. Divide mg/dL by 18 to convert: the ADA pre-meal target of 80–130 mg/dL becomes roughly 4.4–7.2 mmol/L, and the post-meal ceiling of 180 mg/dL becomes 10.0 mmol/L. If you travel or switch devices between unit systems, double-check which one your meter or app is displaying before you react to a number.
Medical Disclaimer: This article is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or qualified healthcare provider with any questions about a medical condition or changes to your diabetes management plan. SweetLife is a tracking and logging tool, not a medical device, and does not provide medical advice.