Fasting blood sugar test: fasting glucose normal range and results

A fasting blood sugar test measures the glucose in your blood after at least 8 hours without food or drinks other than water. With no recent meal pushing it up, the result shows your baseline, the level your body holds glucose at between meals. It is one of the standard tests used to screen for prediabetes and type 2 diabetes.

What fasting glucose measures

Glucose is the body's main source of energy. It comes from the food you eat, and insulin, a hormone made by the pancreas, moves it from the blood into cells. Normally the two rise and fall together. After a fast, both settle at a steady level set by a feedback loop between them, and that level is what this test reads.

A laboratory measures glucose in plasma or serum from a vein. The American Diabetes Association (ADA) notes that results differ with the type and source of the sample, so a finger-prick meter reading and a laboratory result are not directly interchangeable.

Fasting glucose normal range

The ADA uses these bands for adults who are not pregnant.

Other bodies set the lines differently. The World Health Organization starts impaired fasting glucose at 6.1 mmol/L (110 mg/dL), and NICE in the UK treats 5.5 to 6.9 mmol/L as high risk. At the low end, the ADA counts glucose below 3.9 mmol/L (70 mg/dL) as low in people with diabetes, and notes that this is around the level where the body's alarm response to falling glucose begins in people without it.

Ranges vary between laboratories and methods, and a result is read with your history and other results, so the range printed on your own report is the one to read against. One result in the diabetes range is not a diagnosis by itself: without clear symptoms, the ADA asks for two abnormal results, from the same test repeated or from two different tests.

What a high result usually points to

A fasting glucose in the impaired range usually points to prediabetes, and one at 7.0 mmol/L or above, once confirmed, meets the ADA's criterion for diabetes. MedlinePlus also lists other causes: an overactive thyroid, pancreatitis, stress from surgery, serious illness or injury, adrenal conditions such as Cushing's syndrome, and some medicines, including certain steroids, antipsychotics, beta-blockers and statins. A sample taken after eating will also read high.

A doctor will typically repeat the fasting glucose, or check HbA1c or an oral glucose tolerance test, before drawing any conclusion. Under ADA criteria, two results above the threshold, at the same time or on different days, confirm a diagnosis.

What a low result usually points to

In people without diabetes, a low fasting glucose is uncommon. When it happens, MedlinePlus lists causes such as liver or kidney disease, an underactive adrenal, pituitary or thyroid gland, malnutrition, alcohol use disorder and some medicines. In people treated for diabetes, the Endocrine Society notes that insulin and medicines that make the pancreas release insulin are the most common cause.

A low number on paper is not always low in the body: blood cells keep using glucose in a sample that is not processed promptly, so a delayed sample can read falsely low. The Endocrine Society advises investigating low glucose when symptoms, a low measured glucose and relief once glucose is raised all line up. A doctor may then measure glucose, insulin and C-peptide during an episode.

What moves fasting glucose

• An incomplete fast. Food or a sweet drink within 8 hours raises it.
• Stress, illness and activity. The ADA lists recent physical activity, illness and acute stress as factors that change glucose.
• Time of day. Glucose follows a daily rhythm, so a morning fasting result and an afternoon one are not the same test.
• Alcohol and smoking. Both are on the ADA's list of factors that affect glucose results.
• Medicines. According to MedlinePlus, some raise glucose (certain steroids, antipsychotics, beta-blockers and statins) and some lower it (certain ACE inhibitors, quinolone antibiotics and malaria medicines).
• Pregnancy. Glucose is read against different criteria in pregnancy, and pregnant women are usually checked for gestational diabetes between weeks 24 and 28.
• Sample handling. Delay before the plasma is separated lowers the result. Depending on the method, haemolysis, very high triglycerides and very high bilirubin can interfere.

Because so much moves it, the ADA notes that fasting glucose varies more from day to day in the same person than HbA1c does.

Preparing for the test

Fast for at least 8 hours before the sample, with water allowed. Most people fast overnight and give the sample in the morning, which also keeps repeat results comparable. A hard workout just before the test can shift the result.

Tell the person taking the sample if you have diabetes or take medicines that affect glucose, if you are pregnant, or if you have been unwell recently. Any change to a medicine before the test is a decision for the doctor who prescribed it.

How Clare's panel handles it

In Clare's panel, fasting glucose is measured by the lab on the fasting sample. Clare also uses it in two calculated markers: HOMA-IR, which combines it with fasting insulin, and the TyG Index, which combines it with triglycerides. When Clare opens, each result will sit beside your earlier ones, so a change can be seen as a trend.

Why it matters in the UAE

The International Diabetes Federation estimates that in 2024 about 17.0% of UAE adults aged 20 to 79 had impaired fasting glucose and 20.7% had diabetes (both age-standardised), and that around 64% of adults with diabetes had not been diagnosed. The ADA notes that type 2 diabetes develops gradually, often without clear early symptoms, which is why screening relies on blood tests such as fasting glucose rather than on how someone feels.

Price

Fasting glucose is usually sold within a diabetes panel together with HbA1c. When we read public prices on 11 October 2026, a diabetes panel that included fasting glucose cost from 99 to 299 at 5 UAE providers. Some were offer prices, the dearer packages bundled a doctor's consultation or other tests, VAT was rarely stated, and home collection can add a fee.

Related tests

Fasting glucose is read alongside Hemoglobin A1c (HbA1c), which averages glucose over about three months, and Fasting Insulin, which shows how much insulin it takes to hold glucose at that level. Triglycerides join it in the TyG Index. The article HbA1c, glucose and insulin: reading them together explains how they fit.

Fasting glucose over time

A single fasting glucose is a snapshot of one morning; the pattern across results says more. The ADA suggests repeating screening at least every three years when results are normal, sooner if risk changes, and yearly with prediabetes. Because the ADA describes risk as continuous, a glucose that creeps up over several years, even inside the normal band, is worth raising with a doctor with the results in front of you.

Clare is opening with a waitlist at clare.health.