Diabetes risk is assessed in two steps: a scored questionnaire you can complete at home from your age, waist, weight and habits, and a blood test — fasting glucose or HbA1c — that only a laboratory can give you. The questionnaire estimates how likely you are to develop type 2 diabetes over the coming years. The blood test says whether the process has already started. Our entry on Prediabetes covers the condition itself; this page is about getting your own numbers.
What you need
For the questionnaire half, nothing you cannot do at home:
- A tape measure for waist circumference, taken against skin midway between the lowest rib and the top of the hip bone.
- Height and weight, for body mass index.
- Your age, and whether a parent or sibling has diabetes.
- Honest answers on physical activity, daily vegetables and fruit, blood pressure medication, and whether a doctor has ever recorded a high glucose reading — in pregnancy, during an illness, or at a screening.
For the blood half you need a clinic: a fasting plasma glucose drawn after 8 to 12 hours without food, or HbA1c, which needs no fasting. If the two disagree, a doctor may add a 75 g oral glucose tolerance test: two hours in the waiting room and a second draw.
How the measurement works
Questionnaire scores work the same way: each answer carries points, the points are summed, and the total maps onto an estimated probability of developing type 2 diabetes within about ten years. The best known is FINDRISC, from Finnish cohorts and widely reused since. Age, a larger waist, a higher body mass index, physical inactivity, few vegetables, blood pressure medication, a family history and any past high reading all push the total up.
Waist does most of the work in these scores, which is why a standalone Waist-to-height ratio (WtHR) tracks metabolic risk reasonably well on its own. Combining the questionnaire answers with fasting glucose and HbA1c is what the Risk of developing diabetes tool does: it returns a prediabetes index and a type 2 diabetes index rather than a single verdict, because how likely this is later and whether anything is abnormal now are different questions.
How to read the result
The questionnaire output is a probability, not a state: a high score means screening is warranted, not that you have anything. Blood results are read against published diagnostic bands:
| Test | Normal | Increased risk (prediabetes) | Diabetes range |
|---|---|---|---|
| Fasting plasma glucose | below 100 mg/dL (5.6 mmol/L) | 100–125 mg/dL (5.6–6.9 mmol/L) | 126 mg/dL (7.0 mmol/L) or above |
| HbA1c | below 5.7% | 5.7–6.4% | 6.5% or above |
| 2-hour value in a 75 g glucose tolerance test | below 140 mg/dL (7.8 mmol/L) | 140–199 mg/dL (7.8–11.0 mmol/L) | 200 mg/dL (11.1 mmol/L) or above |
Those are the American Diabetes Association criteria. The World Health Organization sets the lower edge of the impaired fasting glucose band higher, at 110 mg/dL (6.1 mmol/L), so an identical result can be called prediabetes by one standard and normal by the other. A single abnormal value is also not a diagnosis: unless symptoms are obvious, it is confirmed by repeating the test on another day.
What it does not tell you
It does not tell you how the body is failing, only that it is. Fasting glucose and HbA1c stay normal for years while the pancreas compensates by producing more insulin, and neither test sees that compensation. Insulin resistance has to be estimated separately, from insulin or from surrogates such as METS-IR: metabolic score for insulin resistance.
HbA1c is a three-month average and inherits the errors of the red blood cells that carry it: anemia, hemoglobin variants, recent blood loss or transfusion, advanced kidney disease and pregnancy all shift it away from true glucose exposure. It also hides shape — two people with the same HbA1c can have flat readings or large spikes after meals.
The questionnaires carry the population they were built in. FINDRISC came from middle-aged Finnish adults, and the body mass index and waist points it assigns fit that group; people of South Asian and East Asian ancestry develop Type 2 diabetes at lower body weights, so a reassuring score can understate risk.
These tools are also aimed at type 2 diabetes. They do not identify type 1, which can begin in adults, the monogenic forms, or diabetes secondary to another disease or medication. Rapid weight loss, heavy thirst and frequent urination are not questionnaire material — they are a reason to see a doctor now. A risk score also says nothing about damage already done to eyes, nerves or kidneys.
Related reading
- How to Improve Metabolic Health: A Practical Guide
- Which Blood Tests Reflect Aging and How to Read Them
- Glycated hemoglobin (HbA1c)
- Insulin resistance
Disclaimer. This article is for information only and does not replace medical advice. Talk to a qualified clinician before changing anything about your health.