What are normal blood sugar levels?
Below 5.5 mmol/L fasting, if you don’t have diabetes. Healthy people spend most of the day between 3.9 and 7.8. But one reading rarely settles anything. Your GP usually checks a different test.
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What is a normal fasting blood sugar level?
Below 5.5 mmol/L. NHS labs class a fasting level of 3.0 to 5.4 as normal. Fasting means over 8 hours with only water.
From 5.5 to 6.9, NICE says your risk of type 2 diabetes is high. The NHS calls this prediabetes: higher than normal, but not high enough for diabetes.
At 7.0 or more, a lab test is in the diabetes range. If you have no symptoms, NICE says to do a second blood test first.
- Below 5.5 mmol/LNormal, without diabetes.
- 5.5 to just under 7 mmol/LHigher than normal. NICE: high risk of type 2.
- 7 mmol/L or aboveDiabetes range. A second test confirms it if you have no symptoms.
Sources: NHS lab (UH Sussex); NICE PH38; Diabetes UK
Some reports still use older WHO cut-offs, where up to 6.0 counts as normal. So check the range printed on your own result.
On 5.5 or more? Ask your GP what your result means for you. More on the lab test in our glucose blood test guide.
What is a normal blood sugar reading at other times?
It depends on when you test and what you last ate. Each test has its own line.
| Test | Normal (no diabetes) | Diabetes range |
|---|---|---|
| Fasting, 8 hours with only water | Below 5.5 mmol/L | 7.0 or more (repeat test if no symptoms) |
| Random lab test, any time of day | Below 6.0 mmol/L | 11.1 or more, with symptoms |
| 2 hours after the lab sugar drink | Below 7.8 mmol/L | 11.1 or more |
| HbA1c, your 2 to 3 month average | Below 42 mmol/mol | 48 or more |
Sources: NHS lab (UH Sussex); NHS lab: sugar drink test; Diabetes UK
A random lab result over 6.0? The lab advice is to do a fasting test next.
There’s no official normal level after an ordinary meal. The 7.8 line comes from the sugar drink test. See blood sugar after eating for what a meal does.
What is an average glucose level?
About 5.4 to 5.5 mmol/L, in one US study of 153 healthy, non-obese people aged 7 to 80 without diabetes. They wore a glucose sensor for up to 10 days.
| Measure | Healthy people on a sensor |
|---|---|
| Average blood sugar | 5.4 to 5.5 mmol/L (5.8 if over 60) |
| Time between 3.9 and 7.8 | About 96% of the day |
| Time above 7.8 | About 30 minutes a day |
| Time below 3.9 | About 15 minutes a day |
Source: Shah et al, 2019 (US study)
So a short rise after food is normal. Diabetes UK says blood sugar goes up and down through the day, with bigger swings in people with diabetes.
US sites use mg/dL. In the same study, 70 mg/dL is 3.9 and 140 is 7.8.
Thinking of buying a sensor? Diabetes UK says it can’t diagnose diabetes or prediabetes. Read glucose monitors without a finger prick first.
Is one high reading a sign of diabetes?
Not on its own. A one-off high usually isn’t harmful either. The NHS says it’s not usually a serious problem if your sugar is sometimes slightly high for a short time.
The test your GP leans on is HbA1c. Diabetes UK calls it the main test for type 2 diabetes.
A single reading is a photo. HbA1c is closer to a film: your average over the last 2 to 3 months. One odd photo doesn’t mean you have diabetes.
Your GP usually confirms a high reading with a lab test, most often HbA1c.
What usually happens after a high reading
- 1
See your GP
Especially if you have symptoms or a higher risk.
- 2
Lab blood test
Usually HbA1c. A home finger prick needs a lab test to confirm it.
- 3
Second test
If the result is in the diabetes range and you have no symptoms.
- 4
Your result
HbA1c 42 to 47 is prediabetes. 48 or more is diabetes.
Sources: NHS; Diabetes UK; NICE PH38
What to do with your blood sugar reading
- Note the time and when you last ate. Fasting means over 8 hours with only water.
- Random lab result over 6.0? Ask your GP about a fasting test.
- Fasting 5.5 to 6.9? Ask your GP whether you need an HbA1c test.
- Fasting 7.0 or more, or 11.1 or more at any time? Book a GP appointment.
- A home sensor can’t tell you if you have diabetes. Only a lab blood test can.
- Aged 40 to 74 with no existing health condition? Ask your GP surgery or pharmacy for a free NHS Health Check.
Sources: NHS lab (UH Sussex); Diabetes UK; NHS
Got your HbA1c back? See normal HbA1c levels and the prediabetes blood test.
What is a low blood sugar level?
Usually below 4 mmol/L. The NHS says low blood sugar mostly affects people who take insulin or some other diabetes medicines. It’s rare without diabetes.
Signs include feeling hungry, dizzy, anxious or irritable, sweating, shaking, tingling lips and a pounding heart. You may also feel tired or weak, confused or have blurred vision.
No diabetes but get these signs? See a GP.
Have diabetes? Follow the diabetic blood sugar levels guide, and never stop or change a prescribed medicine without your prescriber.
When to speak to a GP
Not everyone with type 2 diabetes has symptoms. Book an appointment if:
- You have signs of high blood sugar, like feeling very thirsty, peeing a lot, feeling weak or tired, blurred vision or losing weight, and you have no diabetes diagnosis.
- You don’t have diabetes and get signs of low blood sugar, such as shaking, sweating, a fast heartbeat and feeling confused.
- Your fasting reading is 7.0 or more, or any reading is 11.1 or more. A lab test needs to confirm it.
- You may have a higher risk: you’re white and over 40, or over 25 and South Asian, Chinese, Black African or Black Caribbean. Or a parent, brother or sister has type 2, you’re overweight and not very active, or you have a condition that raises your risk, such as high blood pressure.
Think your sugar is high? Call 999 or go to A&E if you feel sick, are being sick or have stomach pain, or you’re breathing faster than usual.
The same goes for a racing heart or breath that smells fruity. Or if you feel drowsy, struggle to stay awake, feel confused or find it hard to concentrate.
So does a high level of ketones. That’s a sign of a serious diabetes problem, and your care team may ask you to test your blood or pee for them. Don’t drive yourself to A&E.
Call 999 if someone with very low blood sugar is unconscious or not responding normally.
A glucagon injection is an emergency medicine that raises blood sugar. For them, call 999 if it isn’t available or you don’t know how to use it.
Also call if they haven’t recovered 10 minutes after it, or they’ve been drinking alcohol. See the NHS hypo page.