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How to Get Tested for Prediabetes: Tests and What to Ask

Prediabetes is diagnosed using a fasting plasma glucose test or a hemoglobin A1c — both can be ordered at a routine primary care visit with no specialist referral required. The USPSTF recommends screening adults aged 35 to 70 who are overweight or obese; other risk factors may lower that threshold.

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What tests screen for prediabetes?

There are three accepted blood tests for diagnosing prediabetes. All three are equivalent for clinical purposes; the choice depends on convenience and your clinician's preference [1, 2]:

1. Fasting plasma glucose (FPG) - Requires 8 hours of fasting before the blood draw (water is fine) - Prediabetes range: 100–125 mg/dL - Diabetes: 126 mg/dL or above on two separate occasions

2. Hemoglobin A1c (HbA1c) - No fasting required — can be drawn at any time of day - Reflects average blood sugar over the past 2–3 months - Prediabetes range: 5.7%–6.4% - Diabetes: 6.5% or above - Limitations: A1c can be falsely low or high with certain blood conditions (sickle cell trait, iron deficiency anemia, recent blood transfusion); in these situations, fasting glucose is more reliable 2

3. Oral glucose tolerance test (OGTT) — 2-hour - A fasting blood draw, then a standardized glucose drink, then a second draw two hours later - Prediabetes: 140–199 mg/dL at 2 hours - Diabetes: 200 mg/dL or above - More sensitive than FPG or A1c for detecting impaired glucose tolerance, but less convenient; used more routinely in pregnancy screening 2

Who should be screened for prediabetes?

The US Preventive Services Task Force recommends screening adults aged 35 to 70 who have overweight or obesity 3. The ADA uses a broader set of indications — if you have any of the following risk factors, testing is appropriate at any age 2:

  • Overweight or obese (BMI 25 or above; 23 or above in people of Asian ancestry, as risk occurs at a lower BMI)
  • Family history of type 2 diabetes in a first-degree relative
  • History of gestational diabetes or delivering a baby over 9 pounds
  • Polycystic ovary syndrome (PCOS)
  • Hypertension or on blood pressure medication
  • High triglycerides or low HDL cholesterol
  • History of cardiovascular disease
  • Long-term use of corticosteroids, antipsychotics, or certain other medications that raise blood sugar
  • Physically inactive lifestyle
  • Race and ethnicity: Black, Hispanic/Latino, Indigenous, Pacific Islander, and some Asian American populations have higher rates of type 2 diabetes at comparable BMI levels 2

If initial testing is normal and you have ongoing risk factors, repeat testing every one to three years is generally recommended 2.

How do I ask my doctor to test me for prediabetes?

You can be direct: "I'd like to be screened for prediabetes. Can we check a fasting glucose and A1c at my next visit?" Most primary care clinicians will order these readily, particularly if you mention risk factors.

Practical tips: - Schedule a fasting appointment — early morning blood draws are most convenient for fasting tests; many labs open at 7 or 8 a.m. - Mention your family history — a parent or sibling with type 2 diabetes is one of the stronger risk indicators - Bring your medication list — corticosteroids, antipsychotics, and some HIV medications raise blood sugar; your clinician needs this context - Mention recent changes — significant weight gain, new sedentary habits, or high stress can all shift glucose toward prediabetes territory

If you do not have a regular primary care clinician, Gale can help you find one and book the appointment.

What happens if I'm diagnosed with prediabetes?

A prediabetes diagnosis is not a sentence — it is an opportunity. The Diabetes Prevention Program (DPP), a landmark clinical trial, showed that structured lifestyle intervention reduced progression from prediabetes to type 2 diabetes by 58%, compared to 31% with metformin alone, over a three-year follow-up period 4.

The lifestyle elements that drove this result: - Modest weight loss (5–7% of body weight if overweight) - At least 150 minutes per week of moderate-intensity activity - A reduced-calorie, lower-fat dietary pattern

These goals are achievable without extreme measures. CDC-recognized DPP lifestyle change programs are available in many communities and online, and some health plans cover them 3.

Metformin is sometimes prescribed for prediabetes — particularly in younger adults with very high A1c within the prediabetes range, significant obesity, or history of gestational diabetes 2. The decision is individualized and made with your clinician.

Retesting A1c or fasting glucose every 3 to 12 months after a prediabetes diagnosis tracks whether the trend is improving, stable, or worsening 2.

Can I use an at-home test to check for prediabetes?

Consumer finger-stick glucose meters (used by people with diabetes) can give a rough fasting reading, but they have a margin of error of up to 15–20% compared to laboratory venous blood tests. A single home reading in the prediabetes range should always be confirmed by a laboratory fasting glucose or A1c before acting on it.

Several at-home A1c test kits are available without a prescription. These are useful for tracking between appointments, but diagnosis of prediabetes should be confirmed by a clinical lab, and a single A1c below 5.7% should not be treated as a final answer if you have significant risk factors — some labs use slightly different methods.

The most reliable path is a standard lab draw ordered by a clinician, who can interpret results in the full context of your health.

Common questions

Is one high fasting glucose enough to diagnose prediabetes?

A single fasting glucose in the prediabetes range (100–125 mg/dL) is enough to warrant follow-up, but the ADA recommends confirming with a repeat test on a different day unless the reading is clearly in the diabetes range. Inconsistency between a single fasting glucose and A1c can also prompt a second test.

Does prediabetes always become type 2 diabetes?

No. With lifestyle changes, many people with prediabetes return their glucose to the normal range and never develop diabetes. Even those who do progress can extend the time before diabetes develops by years. Prediabetes is most useful as a window for action.

Can I have prediabetes without any symptoms?

Yes. Prediabetes typically causes no symptoms. This is precisely why screening based on risk factors — rather than waiting for symptoms — matters. High fasting glucose or elevated A1c is found incidentally on blood work in most people who are eventually diagnosed.

What is the CDC's online risk test for prediabetes?

The CDC hosts a brief questionnaire (based on age, weight, family history, activity level, and history of gestational diabetes) that estimates your risk of prediabetes. A positive result does not diagnose anything but indicates whether a blood test is worth pursuing. It is available at cdc.gov/diabetes/prevention.

Talk to a clinician

Nina Osei, NP — Nurse Practitioner

checkups, refills & skin. Gale can match you with a licensed clinician for a visit.

Find care →

When to seek care sooner

  • —Symptoms of diabetes — extreme thirst, frequent urination, unexplained weight loss, blurred vision — warrant prompt testing rather than waiting for a routine screen
  • —A home glucose reading above 200 mg/dL at any time should be evaluated by a clinician soon
  • —Fasting glucose of 126 mg/dL or above on a laboratory test requires follow-up for possible diabetes diagnosis, not prediabetes monitoring

This article provides general health education and does not replace clinical evaluation. Prediabetes testing and management should be overseen by a primary care clinician or endocrinologist. Gale can connect you with one.

References

  1. 1.US Preventive Services Task Force (2021). Screening for Prediabetes and Type 2 Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. doi:10.1001/jama.2021.10403 ✓USPSTF recommendation to screen adults aged 35–70 with overweight or obesity; accepted diagnostic tests for prediabetes
  2. 2.American Diabetes Association Professional Practice Committee (2024). 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2024. Diabetes Care. doi:10.2337/dc24-S002 ✓Diagnostic thresholds for prediabetes (FPG 100–125, A1c 5.7–6.4%, OGTT 140–199), risk factors for screening, repeat testing intervals, and metformin use in prediabetes
  3. 3.American Diabetes Association Professional Practice Committee (2024). 3. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes-2024. Diabetes Care. doi:10.2337/dc24-S003 ✓CDC-recognized DPP programs and lifestyle intervention as first-line for prediabetes management
  4. 4.Knowler WC, Barrett-Connor E, Fowler SE, Hamman RF, Lachin JM, Walker EA, Nathan DM; Diabetes Prevention Program Research Group (2002). Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. doi:10.1056/NEJMoa012512 ✓58% relative risk reduction in progression to diabetes with lifestyle intervention; 31% with metformin; 5–7% weight loss and 150 min/week exercise as the effective intervention

4 sources, numbered by first appearance. General health information, not medical advice — synthetic demonstration content.