Normal blood sugar levels: fasting, after meals and in pregnancy, in mg/dL and mmol/L

Normal blood sugar for adults without diabetes

These are the ranges the WHO uses. Your laboratory prints its own reference range on the report, and your doctor reads the result with your symptoms.

• Fasting (no food for at least 8 hours): below 110 mg/dL (6.1 mmol/L) is normal
• Fasting 110 to 125 mg/dL (6.1 to 6.9 mmol/L): impaired fasting glucose, often called prediabetes
• Fasting 126 mg/dL (7.0 mmol/L) or above: diabetes, confirmed with a repeat test unless you have symptoms
• Two hours after a glucose drink in a laboratory test: below 140 mg/dL (7.8 mmol/L) is normal, 140 to 199 (7.8 to 11.0) is impaired glucose tolerance, and 200 (11.1) or above is diabetes
• A random reading of 200 mg/dL (11.1 mmol/L) or more with thirst, frequent urination or weight loss suggests diabetes and needs a doctor promptly

Does normal blood sugar change with age?

The ranges used to diagnose diabetes are the same for every adult, whatever the age. What changes with age is the target a doctor sets once someone has diabetes: in an older or frail person, the doctor may accept slightly higher readings to avoid dangerous lows. Children's results are read by a paediatrician, and a child who is very thirsty, passing a lot of urine, losing weight or wetting the bed again needs to be seen the same day.

If you have diabetes: the readings to aim for

Your own doctor's targets come first. As a guide, the NHS treats these home readings as high for most people with diabetes:

• Over 7 mmol/L (126 mg/dL) on waking or before a meal
• Over 11 mmol/L (about 200 mg/dL) at least 90 minutes after eating
• Below 4 mmol/L (72 mg/dL) is a low (a hypo) and needs sugar straight away
• HbA1c, the three-month average, is the measure most doctors use to judge control

Blood sugar in pregnancy

Pregnancy changes the numbers. NICE diagnoses diabetes in pregnancy (gestational diabetes) at a fasting level of 5.6 mmol/L (about 100 mg/dL) or above, or 7.8 mmol/L (140 mg/dL) or above two hours after a glucose drink, usually tested at 24 to 28 weeks in women at higher risk. These are lower than the levels used outside pregnancy, so a result that would be normal for anyone else can matter in pregnancy. Ask your antenatal team to read it.

Getting an accurate reading

For a fasting test, eat nothing for at least 8 hours beforehand; water is fine. A home meter is useful for following diabetes but is not used to diagnose it: a laboratory fasting blood sugar or an HbA1c is. One high reading in someone without symptoms is repeated on another day before anyone is told they have diabetes. Illness, steroids and a very large meal the night before can push a reading up.

Go to a hospital now

A number can wait for a doctor. These cannot. Go to an emergency department for:

• Vomiting, deep or fast breathing, drowsiness or confusion with a high sugar
• A low sugar that does not improve after taking something sugary, or someone too drowsy to swallow safely
• A fit, or being unconscious

Common questions