Home › Biomarkers › Glucose, fasting
A study followed healthy men aged 40 to 59 for 22 years. Men with a fasting glucose above 85 mg/dl had a higher chance of dying from a condition of the heart and blood vessels than the other men.[1]
On this page, you can read what Glucose, fasting is, what the guidelines say about a value that is too low or too high, what affects your value and which other values are best looked at alongside it.
Also known as: blood sugar, fasting blood sugar, fasting plasma glucose, FPG, FBG. At the lab: GLUN.
Glucose, fasting is the amount of sugar in your blood after you have not eaten for a while. Glucose comes from your food and is your body's main source of energy. The hormone insulin helps move glucose from your blood into your cells. For the test, you eat and drink nothing except water for at least 8 hours, and then blood is taken from a vein in your arm.[2, 1]
Too much or too little glucose in your blood can point to a medical condition. A high value can mean that your body cannot make insulin or is less able to use it. It can also point to a problem with the pancreas or the adrenal glands, or to a side effect of some medicines. A low value can point to, among other things, some diseases of the kidneys or the liver, or to the use of certain medicines.[2, 1]
A large study followed healthy middle-aged men for many years. Men whose fasting glucose sat in the upper part of the normal range had a higher chance of dying from a condition of the heart and blood vessels. That remained the case even after other factors such as smoking, blood pressure and fitness were taken into account. The study looked only at men.[2, 1]
When your blood sugar is too high, too much glucose stays in your blood. It does not reach your cells. If it stays that way, it can lead to serious, long-term health problems, such as a heart condition and nerve problems.[2]
There is also an early stage. Your blood sugar is then higher than is healthy for you, but not yet high enough to count as the condition itself.[2]
Severely low blood sugar, left untreated, can lead to major health problems, such as seizures and brain damage.[2]
Your healthcare provider may ask for the test sooner if you have a higher risk of persistently high blood sugar. That can be the case if you are older than 35, are overweight, have high blood pressure, have a family history of it or are active fewer than three times a week.[2]
The lab BioProfile works with, Labplusarts, uses a reference value of 3.5 to 6.0 mmol/l for fasting glucose. The lab calls a level between those limits normal.[3]
| Fasting glucose | What it can mean | Who it is for |
|---|---|---|
| Below 110 mg/dl[1] | Criterion for taking part in the study | Healthy men aged 40 to 59 |
| The three lowest quarters, not above 85 mg/dl[1] | Comparison group in the study | Healthy men aged 40 to 59 |
| Above 85 mg/dl, the highest quarter[1] | Higher chance of dying from a condition of the heart and blood vessels; relative risk 1.4 after taking other factors into account | Healthy men aged 40 to 59 |
| All values in the study[1] | Death from other causes was not linked to the value | Healthy men aged 40 to 59 |
Source: Bjørnholt and colleagues, 1999. Healthy men aged 40 to 59 only, followed for 22 years. Values in mg/dl, the unit used in the study.[1]
Blood sugar that is too low is often caused by certain medicines that lower blood sugar, such as insulin. In other people, a low level is much less common. Symptoms can include shaking, hunger, tiredness, feeling dizzy or confused, headache and a fast heartbeat.[2]
A blood sugar level that is too high can cause symptoms such as more thirst, needing to pee often, blurred vision, tiredness, small wounds that are slow to close and a numb or tingling feeling in your feet or hands. In the study of men who were well, the top quarter was above 85 mg/dl, still within the normal range.[2, 1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Glucose comes from what you eat. A random glucose test can be done at any time, including after eating. The fasting test, by contrast, needs a period without food, so that what you have eaten does not affect the result.[2]
Some medicines can raise your blood sugar in some people, such as certain types of steroids, antipsychotics, beta blockers and statins. Others can lower it, such as certain ACE inhibitors and antibiotics from the quinolone group.[2]
Pregnant people can develop high blood sugar. If you are pregnant, you will probably have a blood glucose test between week 24 and week 28.[2]
Glucose, fasting is included in BioProfile 77, 87, 121 and 150.[4]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
