Your report says one sugar number is a little high, and now you are wondering whether you have diabetes. Let me explain what each blood sugar test tells us, and how we decide which one to use.
The three tests, in plain words
Fasting blood sugar. Blood is taken after at least 8 hours with no food or sugary drinks. A result of 126 mg/dL or above is in the diabetes range. A result of 100 to 125 mg/dL is called prediabetes.
HbA1c. This shows your average blood sugar over roughly the last three months, and you do not need to fast for it. 6.5% or above is in the diabetes range. 5.7% to 6.4% is prediabetes.
Glucose tolerance test. You give a fasting sample, then drink a measured glucose solution, and blood is taken again two hours later. A two-hour value of 200 mg/dL or above is in the diabetes range, and 140 to 199 mg/dL is prediabetes.
One high result is not a diagnosis
If there are no clear symptoms, a single abnormal result is usually repeated, or two different tests are done together, before we say you have diabetes. A recent illness, or not fasting properly, can push a number up. So please do not panic over one report, and please do not ignore it either.
Which test is right for you?
HbA1c is convenient because it needs no fasting. But in conditions that affect red blood cells, such as anaemia, it can be less reliable. In that case I rely more on the blood sugar tests. Your doctor chooses based on your history.
One more point. A finger-prick machine is very useful for day-to-day monitoring, but guidelines ask that the diagnosis itself is made with a laboratory test.
Who should get tested?
The American Diabetes Association recommends that all adults are screened from age 35. Screening should start earlier if you are overweight and have other risk factors, such as a family history of diabetes or high blood pressure. If you already have prediabetes, we repeat the test at least once a year.
What I would suggest
Keep your old reports and bring them with you, because the trend matters as much as the latest number. Do not start a crash diet or a supplement on your own because of one result. Get the test repeated and let us look at the whole picture.
If you would like to talk through your own reports, you can call the clinic on +91 77298 87888 or use the contact page.
Your family doctor,
Akhila Reddy
MBBS, DNB (Family Medicine) | TSMC Reg. No. APMC/FMR/74261
AMC Hospital, Gopanpally, Gachibowli, Hyderabad
This article is general health information. It does not replace a consultation, and it is not a diagnosis or treatment plan for you. If you have symptoms or a report you are worried about, please see a doctor. For a medical emergency, call 108.
References
- American Diabetes Association. Standards of Care in Diabetes, Classification and Diagnosis of Diabetes (diagnostic criteria for A1C, fasting plasma glucose and OGTT; screening from age 35).
- Diabetes Care 2023;46(10):e151-e199, Table 4: criteria for the diagnosis of diabetes (adapted from the ADA), including confirmation by repeat testing and laboratory-based HbA1c.