Blood sugar levels chart: Normal, prediabetes and diabetes ranges

Key takeaways

Normal fasting blood sugar is 70-99 mg/dL (3.9-5.5 mmol/L) for adults without diabetes.

Prediabetes runs 100-125 mg/dL (5.6-6.9 mmol/L). Diabetes needs 126 mg/dL or higher on two separate occasions, or an A1C of 6.5% or higher.

Two hours after a meal, under 140 mg/dL (7.8 mmol/L) is normal. The ADA target for type 2 diabetes is under 180 mg/dL.

Diagnostic cutoffs are the same at every age. After diagnosis, the ADA’s fasting target is 80-130 mg/dL for most non-pregnant adults.

Practice management software like Pabau records every fasting result against the client file and schedules the next recall automatically.

This blood sugar levels chart carries the fasting, after-meal, and A1C cutoffs in one place. Normal fasting blood sugar is 70-99 mg/dL, or 3.9-5.5 mmol/L, after at least eight hours without food.

A result of 100 to 125 mg/dL indicates prediabetes. A result of 126 mg/dL or higher points to diabetes, once a second test confirms it.

Reading the number is the easy part. The work in a practice comes after it. You need a confirmation test, a result documented against the right fasting interval, and a recall the patient actually attends.

The chart also corrects an error you will see in age-based versions, which show the diagnostic cutoff rising after 65. Every range matches what the ADA publishes, so it lines up with the reference values already sitting in your metabolic health records.

What a fasting blood sugar test measures?

A fasting blood sugar test measures glucose after the patient has taken nothing but water for at least eight hours. It isolates the body’s baseline glucose production, with no recent meal skewing the reading. That makes it the standard first screen for diabetes and prediabetes.

Random blood glucose moves all day with food, stress, and activity. A fasting sample instead shows how well the pancreas holds glucose steady overnight. Normal fasting blood sugar therefore says more about metabolic health than any single daytime reading.

Results come back in one of two units, depending on where you practice. The US and several other countries use mg/dL (milligrams per deciliter). The UK, Europe, Australia, and Canada use mmol/L (millimoles per liter). To convert, multiply mg/dL by 0.0555, or mmol/L by 18.0182. Never round the converted value in a clinical record.

Normal blood sugar levels chart: What each range means

The blood glucose levels chart below is the reference standard used by the American Diabetes Association (ADA) and the World Health Organization (WHO). Every cutoff is checked against the current ADA Standards of Care. Both units sit side by side, so nobody has to multiply by 0.0555 mid-appointment.

Important diagnostic note: one raised fasting glucose does not diagnose diabetes. The ADA asks for a fasting result of 126 mg/dL (7.0 mmol/L) or higher on two separate occasions. A single random glucose of 200 mg/dL alongside symptoms also confirms it, as does an A1C of 6.5% or higher.

Postprandial (after-meal) glucose targets

Fasting glucose is the screening test, but it says nothing about how a patient handles a meal. Postprandial glucose, taken two hours after eating, fills that in for anyone already on treatment.

How A1C maps to average glucose

The A1C test measures glycated hemoglobin, which reflects average blood glucose over roughly three months. It sits alongside fasting glucose for both screening and monitoring. The ADA-validated conversion below turns an A1C result into an estimated average glucose.

Normal blood sugar levels chart by age: Do the ranges change?

No. The diagnostic thresholds are identical at every age. A fasting result of 100 mg/dL means prediabetes in a 22-year-old and in an 80-year-old, and 126 mg/dL means diabetes in both.

Search for a blood sugar level age 40 to 50 chart and you will find dozens. The same goes for a blood sugar level age 50 to 60 chart. Each one nudges the cutoff up a little for the older bracket.

Those charts have confused two separate things. What the ADA individualizes by age and health status is the glycemic target set after diagnosis, not the threshold used to reach that diagnosis.

Targets loosen for older patients with several conditions or a limited life expectancy. A hypoglycemic episode does more damage to them than a slightly high reading. The table below shows where the ADA lands for each group.

Children and adolescents with type 1 diabetes usually work to an A1C below 7% as well. That target moves with their hypoglycemia risk and how much support they have at home. For the full picture, read the current ADA Standards of Care.

Older patients on insulin or a sulfonylurea are also the group most likely to fall after a hypoglycemic episode. Pairing the annual diabetes review with a fall risk assessment catches that early.

What level of blood sugar is dangerous?

A reading at or above 400 mg/dL, or below 54 mg/dL, is a medical emergency. The thresholds below answer what level of blood sugar is dangerous enough to escalate on the day, rather than at the next appointment.

• Severe hyperglycemia (400 mg/dL / 22.2 mmol/L or above): risk of diabetic ketoacidosis or a hyperosmolar hyperglycemic state. Seek immediate medical care.
• Severe hypoglycemia (below 54 mg/dL / 3.0 mmol/L): risk of seizure, loss of consciousness, or lasting neurological damage. Give fast-acting glucose at once. Call emergency services if the patient cannot self-treat.
• Persistent hyperglycemia (above 250 mg/dL / 13.9 mmol/L for more than two hours): needs medical review. It often signals too little insulin, or a medication that needs adjusting.

Signs of high blood sugar (hyperglycemia)

High blood sugar symptoms appear when glucose stays elevated for a stretch, rather than after a single spike. Catching them early is often what brings an undiagnosed patient through the door.

• Excessive thirst (polydipsia)
• Frequent urination (polyuria), especially at night
• Fatigue or weakness unrelated to activity
• Blurred vision or difficulty focusing
• Slow-healing cuts or repeated infections
• Fruity-smelling breath, which signals ketone production in severe hyperglycemia

Signs of low blood sugar (hypoglycemia)

Low blood sugar symptoms come on in minutes, not hours. Teach patients and their families to act on these signs without waiting for a reading.

• Shakiness, trembling, or nervousness
• Sweating, with cold or clammy skin
• Rapid or irregular heartbeat (palpitations)
• Intense hunger, sometimes with nausea
• Trouble concentrating, confusion, or irritability
• Tingling around the mouth
• Loss of consciousness in severe cases

Treatment follows the 15-15 rule. The patient takes 15 grams of fast-acting carbohydrate, such as glucose tablets or juice, waits 15 minutes, then rechecks. Repeat if the reading is still below 100 mg/dL. Logging each episode on a digital form shows how often it is happening before the next medication review.

How to run the test

Most unreliable readings trace back to preparation rather than to the laboratory. Fasting before blood work is where patients slip up most often, so walk them through these five steps.

1. Fast for eight to ten hours. Nothing but water after dinner the night before. Morning appointments are the norm for exactly this reason.
2. Check medication timing. Ask whether the patient took insulin or an oral agent that morning. Some are withheld before the draw and others are not, so check the diabetes medication list and record what was taken.
3. Take the sample. A venous draw from the arm is standard. A fingerstick capillary sample is acceptable where the ordered test allows it.
4. Label and transport. Mark the sample with the patient’s name, date, and time. Send it to the laboratory promptly, because glucose degrades in a sitting sample.
5. Report the result. Values return in mg/dL or mmol/L, usually within 24 hours. File the number and the fasting interval together in the client record.

How to lower fasting blood sugar after a prediabetes result

The two changes that move fasting glucose most are weight loss and activity. The ADA points to losing 5% to 7% of body weight, plus 150 minutes of moderate exercise a week.

A prediabetes result is the point where that work pays off most. The interventions below are the ones the ADA backs for lowering fasting glucose and slowing progression.

• Increase physical activity. Aim for 150 minutes a week of moderate aerobic exercise. It improves insulin sensitivity and lowers fasting glucose.
• Modify the diet. Cut refined carbohydrates and added sugars, and build meals around whole grains, lean protein, and vegetables. A healthy meal plan gives the patient something concrete to follow.
• Refer for nutrition support. A registered dietitian can fit the advice around how the patient actually eats. Record what was agreed in a nutrition care plan.
• Address weight where it applies. Losing 5% to 7% of body weight shifts fasting glucose more than most single changes. Practices running a structured weight loss program already track this alongside glucose.
• Monitor at a set interval. Patients with prediabetes or diabetes should check fasting glucose quarterly, or more often if directed. A client portal lets them log readings between visits.
• Protect sleep and manage stress. Both raise cortisol and blunt glucose control. Seven to nine hours a night is the target worth pushing for.
• Keep medication on schedule. Consistency matters most with metformin and insulin. Automated reminders lift adherence without adding calls for your team.

How Pabau turns a glucose result into a booked follow-up?

In most practices the chart is the easy bit. The result arrives by email or fax, someone types it into the record, and the recall depends on a person remembering to book it. Prediabetes patients slip through first, because nothing about their result feels urgent on the day.

Practice management software like Pabau closes that loop. A digital glucose form drops the reading straight into the client file, so there is no retyping and no loose lab slip. Each result sits next to the last one, which makes a slow climb from 98 to 112 mg/dL obvious at a glance.

You then set the rule once for the prediabetes pathway. Any fasting result between 100 and 125 mg/dL books a three-month retest. The patient gets the reminder, and whoever ordered the test picks up a task.

Anyone who has not rebooked by the due date lands on one overdue list. Your team spends its morning calling the eight patients who are genuinely late, instead of working out who they are.

Track every glucose result and never miss a recall

Pabau records fasting and A1C results against the client file, charts the trend across visits, and schedules the retest automatically. Your team stops rebuilding the picture by hand at every appointment.

Book a demo

Conclusion

The thresholds themselves are settled and easy to look up. Practices get caught out by treating one raised reading as a diagnosis, or by using a treatment target as though it were a diagnostic cutoff. Keep those two apart and the rest of the pathway follows.

The follow-up is the other half of it. A prediabetes result only pays off if the patient comes back, and that rests on a recall system rather than goodwill. Print the glucose levels chart for the treatment room. Then check that a recall interval is set for every patient sitting between 100 and 125 mg/dL.

Book a demo to see how Pabau logs each glucose result and books the retest before the patient leaves.

Continue your research

Need somewhere for patients to record readings? The blood glucose log gives them a structured sheet to fill in between appointments.

Due a complication screen? The diabetes eye exam template covers the retinal check that belongs in the same annual review.

Is a fasting result borderline? Our guide to the glucose tolerance test explains when a second test earns its place.

Setting a target after diagnosis? The A1C goals by age chart shows how the ADA loosens targets for older patients.

Patient asking what to eat? The type 2 diabetes diet food list turns general advice into a shopping list.

Frequently asked questions