Normal Blood Sugar Levels: Fasting, After Meals, HbA1c and Targets for Diabetes

Knowing the normal blood sugar (glucose) range helps you understand test results, spot problems early and, if you have diabetes, judge how well your treatment is working. Values are reported in mg/dL (used in many countries) or mmol/L (used in Sri Lanka's hospitals and the UK). To convert, divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18.

Normal blood sugar ranges for adults without diabetes

• Fasting (no food for at least 8 hours): 70-99 mg/dL (3.9-5.5 mmol/L)
• 2 hours after eating: below 140 mg/dL (7.8 mmol/L)
• Random (any time): usually below 140 mg/dL (7.8 mmol/L)
• HbA1c: below 5.7% (39 mmol/mol)

Prediabetes ranges

• Fasting: 100-125 mg/dL (5.6-6.9 mmol/L)
• 2 hours after a 75 g glucose drink: 140-199 mg/dL (7.8-11.0 mmol/L)
• HbA1c: 5.7-6.4% (39-47 mmol/mol)

Prediabetes is an important warning. Without changes, a large proportion of people progress to type 2 diabetes, but lifestyle change can return blood sugar to normal. See our guide on whether diabetes can be cured or reversed.

Diabetes ranges

Diabetes is diagnosed when any of these are found, and usually confirmed by repeating the test on another day (unless there are clear symptoms):

• Fasting plasma glucose: 126 mg/dL (7.0 mmol/L) or higher
• 2-hour glucose tolerance test: 200 mg/dL (11.1 mmol/L) or higher
• HbA1c: 6.5% (48 mmol/mol) or higher
• Random glucose: 200 mg/dL (11.1 mmol/L) or higher with typical symptoms such as thirst, frequent urination and weight loss

What is HbA1c?

HbA1c measures the percentage of haemoglobin in red blood cells that has sugar attached. Because red cells live about three months, it shows your average blood sugar over that time. Use our HbA1c calculator to convert your result into an estimated average glucose (eAG).

Some conditions make HbA1c less reliable, including anaemia, recent blood loss or transfusion, kidney disease and inherited haemoglobin disorders such as thalassaemia, which are relevant in Sri Lanka. In these cases doctors may rely on glucose tests or fructosamine.

Targets if you have diabetes

Targets should be personalised. Many adult guidelines suggest:

• Fasting or before meals: 80-130 mg/dL (4.4-7.2 mmol/L)
• 1-2 hours after the start of a meal: below 180 mg/dL (10.0 mmol/L)
• HbA1c: about 7% (53 mmol/mol) or lower for many adults

Older adults, people with other serious illnesses, or those at risk of low sugar may have a looser target, for example HbA1c 7.5-8.5%. Young people and those newly diagnosed may aim lower. Your doctor will set your goals.

Blood sugar in pregnancy

For women with gestational diabetes, common targets are fasting below 95 mg/dL (5.3 mmol/L), 1 hour after meals below 140 mg/dL (7.8 mmol/L), or 2 hours below 120 mg/dL (6.7 mmol/L). Local hospital protocols may differ slightly, so follow your obstetrician's advice.

Children

Normal fasting glucose in children is similar to adults. Children with type 1 diabetes usually have individual targets set by their paediatric team, often around 70-180 mg/dL (3.9-10.0 mmol/L) with HbA1c below 7%.

Low blood sugar (hypoglycaemia)

Low blood sugar is below 70 mg/dL (3.9 mmol/L), and below 54 mg/dL (3.0 mmol/L) is serious. It happens mainly with insulin or tablets such as gliclazide and glibenclamide.

• Symptoms: shaking, sweating, hunger, palpitations, headache, irritability, confusion.
• Treatment (if the person is awake): 15 g of fast sugar, such as 3-4 glucose tablets, half a cup of fruit juice or a tablespoon of sugar in water. Recheck after 15 minutes and repeat if needed, then eat a snack.
• If unconscious or unable to swallow: do not put food in the mouth. Call for emergency help; glucagon may be given if available.

High blood sugar (hyperglycaemia)

Sugar levels above target can cause thirst, frequent urination, tiredness and blurred vision. Dangerous complications are diabetic ketoacidosis (mostly in type 1) and hyperosmolar state (older people with type 2). Seek urgent care for vomiting, abdominal pain, fast deep breathing, drowsiness or very high readings that do not fall.

How to test accurately

1. Wash and dry your hands. Sugary or wet fingers give false results.
2. Use the side of the fingertip, rotate sites, and do not squeeze hard.
3. Check the test strip expiry date and store strips sealed.
4. Record results with time, meals, activity and medicines, and bring the log to your doctor.
5. Do not rely on a meter that has not been checked against a laboratory test now and then.

Things that change blood sugar

Meals rich in carbohydrate, portion size, exercise (usually lowers sugar), illness and infection, stress, poor sleep, alcohol, steroid medicines, and missed or extra doses of diabetes medicines.

When to see a doctor

Get tested if you are over 30-35, have a BMI of 23 or above, high blood pressure, a family history of diabetes, PCOS or past gestational diabetes, or symptoms such as thirst and frequent urination. If you have diabetes, see your doctor if your readings are regularly outside target or you have frequent low sugars. Read our list of early symptoms of diabetes.

References

• American Diabetes Association: Standards of Care in Diabetes, diagnosis and glycaemic targets
• World Health Organization: definition and diagnosis of diabetes mellitus
• International Diabetes Federation: global guideline