Type 2 diabetes is diagnosed using blood tests that show your glucose is in the diabetes range — most commonly an HbA1c, a fasting blood glucose, an oral glucose tolerance test (OGTT), or sometimes a random glucose when symptoms are present.

For many people, the diagnosis is picked up “by accident”. A routine blood test comes back a little high, or an HbA1c is added to a check-up and the result is above the diabetes range. If you know your HbA1c result, try our HbA1c tool to understand what it means in practical terms.

Why does early diagnosis matter? Because Type 2 diabetes affects blood vessels over time. Good glucose control reduces the risk of heart disease, stroke, kidney disease, eye disease and nerve damage — and early treatment is often simpler than late treatment.

What helps most (right now)

Confirm the diagnosis properly (repeat the test or use a second test if needed)
Don’t rely on symptoms — Type 2 diabetes can be present for years without obvious warning signs
Use the “right” test for the situation (HbA1c is useful, but not perfect for everyone)
Clarify the type if the story doesn’t fit (sometimes other diabetes types need different treatment)
Link diagnosis to action: targets, lifestyle, and medications can be personalised once you know where you stand

Start where you are

If you’re here for a specific question, use this quick guide:

If you’re trying to make sense of symptoms → Signs and symptoms of Type 2 diabetes
If you want the “big picture” of diabetes tests → How is diabetes diagnosed?
If you want HbA1c explained (and why it can miss people) → HbA1c to diagnose Type 2 diabetes
If you want a quick practical risk estimate → Diabetes Risk Calculator
If you want the next step after diagnosis → How is type 2 diabetes treated?

If you’d like the global context, see the WHO diabetes fact sheet and the International Diabetes Federation (IDF) Diabetes Atlas.

Diagnosing type 2 diabetes requires blood tests such as HbA1c and fasting glucose

Who should be screened for Type 2 diabetes?

Type 2 diabetes can be present for a long time before symptoms appear. That’s why guidelines recommend screening people who are at higher risk — even if they feel well. The American Diabetes Association (ADA) recommends testing for diabetes in higher-risk groups such as:

Adults with a body mass index higher than 25 (or 23 for some Asian backgrounds) plus additional risk factors such as high blood pressure, abnormal cholesterol, physical inactivity, a history of gestational diabetes or polycystic ovary syndrome (PCOS), heart disease, or a close relative with diabetes.
Adults in mid-life and beyond should discuss screening, and if results are normal, repeat testing every few years (or sooner if weight, symptoms, medications, or health status changes).
Women with a history of gestational diabetes should be screened regularly and in future pregnancies.
Anyone previously found to have “prediabetes” should be tested more frequently, because the risk of progression is higher.

If you’d like a quick, practical estimate of risk and what to do next, use our Diabetes Risk Calculator.

For an overview of screening and diagnostic tests written for patients, you can also read the CDC guide to diabetes tests. In the UK, the NHS diagnosis page is a clear reference point.

How does your doctor confirm it’s Type 2 diabetes (and not something else)?

Most of the time, the diagnosis is straightforward: blood tests fall clearly into the Type 2 diabetes range, and the clinical picture fits. Often (though not always) Type 2 diabetes sits alongside insulin resistance — if that concept is new, you may find our insulin resistance guide helpful.

Where it becomes important to be careful is when results sit near the border, or the story doesn’t fit. In those situations, your doctor may:

repeat the same test on another day to confirm the diagnosis
use a second method (for example HbA1c plus fasting glucose, or fasting glucose plus an oral glucose tolerance test)
consider whether another type of diabetes could be present (for example autoimmune diabetes in adults)

A key point: Type 2 diabetes shouldn’t be diagnosed (or excluded) using only one imperfect snapshot. HbA1c is very useful, but it can miss some people — and it can be misleading in certain situations. That’s why combining tests can give a clearer answer.

If you want a deeper explanation, see: Why HbA1c shouldn’t be the only diagnostic test and our HbA1c units guide.

How this page fits into your learning

My Health Explained is designed to help you understand diabetes over time, not all at once. Most people arrive with one specific question, then build confidence as new questions come up.

This page covers one important part of that picture. You'll see links throughout to related topics that explain why things happen, what options exist, and what tends to help in real life.

If you'd like a broader overview first, start here: What is type 2 diabetes mellitus?.

If something here raises a question, follow the links that feel most relevant and ignore the rest for now. This resource is built to support learning at your own pace.

Next time you are heading to the doctors for your appointment make sure you are ready to ask the questions to gently make sure nothing has been missed or overlooked with this helpful guide that we will send straight to your email inbox.

What are the diagnostic criteria for Type 2 diabetes?

Type 2 diabetes is diagnosed using blood glucose tests that show your levels are consistently above the diabetes threshold. Depending on the test used, your doctor will usually confirm the diagnosis either by repeating the test on a separate day, or by using a second test method that also falls in the diabetes range.

Diagnostic blood glucose levels used to diagnose diabetes
Test	mmol/L	mg/dL
HbA1c	≥ 6.5% (48 mmol/mol)
Fasting plasma glucose	≥ 7.0 mmol/L	≥ 126 mg/dL
2-hour glucose (75 g oral glucose tolerance test)	≥ 11.1 mmol/L	≥ 200 mg/dL
Random plasma glucose + classic symptoms	≥ 11.1 mmol/L	≥ 200 mg/dL

If your results are elevated but do not reach these thresholds, your doctor may describe this as “prediabetes” (also called impaired fasting glucose or impaired glucose tolerance). It’s not Type 2 diabetes yet — but it is a warning sign that risk is rising and you deserve a clear plan. If that’s where you are, see: What is prediabetes and does it matter?

Which test is best for you?

The HbA1c test

The HbA1c test estimates your average glucose over the previous 2–3 months. You don’t need to fast, which makes it convenient. An HbA1c of 6.5% (48 mmol/mol) or higher can indicate diabetes — usually confirmed with a repeat test or a second method if the result is near the threshold.

HbA1c can be less reliable in some situations (for example certain anaemias, recent blood loss, kidney disease, pregnancy, or conditions affecting red blood cells). That’s one reason we often combine it with fasting glucose or an oral glucose tolerance test when we want a clearer answer.

You can also use our HbA1c Converter & Target Tool to understand your result in context.

Fasting blood glucose test

A fasting glucose test measures your blood sugar after an overnight fast. It’s a simple, widely used diagnostic test — and it’s often paired with HbA1c. A fasting glucose of 7.0 mmol/L (126 mg/dL) or higher, confirmed, is in the diabetes range.

Oral glucose tolerance test (OGTT)

In an OGTT, you fast overnight, have a fasting blood test, then drink a 75 g glucose drink. Your blood sugar is checked again two hours later. It can pick up diabetes that fasting glucose or HbA1c may miss in some people. A two-hour glucose of 11.1 mmol/L (200 mg/dL) or higher is diagnostic of diabetes.

Random blood glucose test

A random blood glucose test can be taken at any time. A result of 11.1 mmol/L (200 mg/dL) or higher can indicate diabetes — and it is most convincing when it is clearly high and you have symptoms such as thirst, frequent urination, weight loss or blurred vision. If you feel well and the number is borderline, doctors usually confirm it with fasting glucose, HbA1c or an OGTT.

Do urine tests diagnose Type 2 diabetes?

Urine tests are not usually used to diagnose Type 2 diabetes. Sometimes glucose can spill into urine when blood sugars are very high, but urine testing is less precise than blood tests. If your doctor is concerned about Type 1 diabetes (especially rapid weight loss, ketones, or sudden severe symptoms), they may check urine or blood ketones urgently.

For formal guideline language on classification and diagnosis, you can also refer to the ADA Standards of Care (Diabetes Care journal).

What to do next

If you’ve just been diagnosed, your next step is to turn the result into a clear plan — not panic and not denial. Start by confirming which tests were used (and whether anything needs repeating), then focus on the “big three” that change risk the most: glucose targets, weight/insulin resistance, and cardiovascular protection (blood pressure, cholesterol, smoking, sleep). Most people don’t need to do everything at once. You need the right first steps, done consistently. If you’d like a calm, specialist-led overview of what to prioritise and how treatment is tailored over time, you can join our free Type 2 Diabetes Masterclass.

When should you speak to your doctor (or ask for repeat testing)?

If you have symptoms that worry you — or a result that is “borderline” and doesn’t match how you feel — it’s completely reasonable to ask for a clearer plan. Many people sit in a grey zone for years: not “terrible”, not “ideal”, and not sure what it means. Clarity matters, because clarity is what allows you to act calmly rather than react anxiously.

If you’ve been newly diagnosed with Type 2 diabetes — or you suspect your sugars are rising — it’s worth getting clear answers early. And if you’d like a calm, medically grounded explanation of how specialists think about targets, medications, and long-term risk, you can join our free online Type 2 Diabetes Masterclass.

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How is type 2 diabetes diagnosed?