Type 2 diabetes cannot always be prevented, but many people can substantially lower or delay their risk. The most effective approach is to identify prediabetes early, build sustainable eating and activity habits, improve sleep, avoid tobacco, and address weight or related cardiometabolic risks when appropriate. The main blood sugar tests are A1C, fasting plasma glucose, and a two-hour oral glucose tolerance test. These tests measure different parts of glucose regulation and may not always agree. Testing identifies risk; it does not lower risk by itself. A structured diabetes-prevention program and a clinician-guided follow-up plan turn results into action.
If lab testing is new to you, begin with Ulta Lab Tests' Complete Guide to Lab Tests and Blood Work. For a broader map of glucose, insulin, and cardiometabolic testing, see Diabetes and Prediabetes Blood Tests: A1C, Glucose, Insulin, and C-Peptide.
Type 2 diabetes develops when the body cannot use insulin effectively and, over time, the pancreas cannot make enough insulin to keep blood glucose within a healthy range. This process often develops gradually. Insulin resistance can be present for years before glucose reaches the diabetes range.
Risk is shaped by biology, health conditions, medicines, daily habits, and social or environmental circumstances. Having a risk factor does not mean diabetes is inevitable, and some people develop diabetes without obvious warning signs.
Diabetes also affects some racial and ethnic groups at higher rates in the United States. These differences reflect a complex mix of family history, access to care, food and activity environments, chronic stress, and other social determinants; race is not itself a laboratory measure or a simple biological cause.
The American Diabetes Association recommends risk assessment and testing for adults of any age who have overweight or obesity plus at least one additional risk factor. For other adults, screening should begin by age 35. It also recommends testing at least once every three years when initial results are normal, and at least yearly for people with prediabetes. A clinician may recommend earlier or more frequent testing based on changing risk.1
The U.S. Preventive Services Task Force uses a narrower population recommendation: screen asymptomatic, nonpregnant adults ages 35 to 70 who have overweight or obesity, and offer or refer those with prediabetes to an effective preventive intervention.2 These recommendations are not contradictory; they come from organizations using different evidence-review methods and scopes. Your clinician can apply the guidance to your health history.
Do not wait for routine screening if you develop increased thirst, frequent urination, unexplained weight loss, blurred vision, unusual fatigue, recurrent infections, or slow-healing sores. Prompt medical assessment is appropriate. Vomiting, abdominal pain, deep or rapid breathing, confusion, severe weakness, or loss of consciousness requires urgent care.
Three glucose-based tests are used to identify prediabetes and diagnose diabetes in nonpregnant adults. No single test is best for every person. A clinician may choose a test based on fasting status, symptoms, pregnancy, medicines, medical conditions, and whether A1C is likely to be reliable.
| Test | What it reflects | Prediabetes range | Diabetes range |
|---|---|---|---|
| A1c Test | Approximate average glucose exposure over the previous 2 to 3 months; fasting is not required | 5.7% to 6.4% | 6.5% or higher |
| Glucose Test performed fasting | Plasma glucose after no caloric intake for at least 8 hours | 100 to 125 mg/dL | 126 mg/dL or higher |
| Glucose Tolerance Test 2 Specimens 75g | Fasting glucose and the glucose response 2 hours after a 75-gram glucose drink | 2-hour glucose of 140 to 199 mg/dL | 2-hour glucose of 200 mg/dL or higher |
These thresholds come from the American Diabetes Association's 2026 Standards of Care.1 In a person without unequivocal hyperglycemia, a result in the diabetes range generally needs confirmation with a repeat abnormal result. A random plasma glucose of 200 mg/dL or higher can support a diagnosis when classic hyperglycemia symptoms or a hyperglycemic crisis are present. Laboratory criteria for pregnancy and children require separate clinical guidance.
A1C can be misleading when red blood cell turnover or hemoglobin is altered. Examples include some anemias, recent blood loss or transfusion, certain hemoglobin variants, pregnancy, kidney disease, and medicines that affect red blood cells. If A1C and glucose results disagree, do not average them or assume one is correct. Ask whether repeat testing or another method is appropriate. For a deeper explanation, read why A1C, fasting glucose, OGTT, kidney, and lipid testing must be read together.
A combined Hemoglobin A1c and Glucose Panel can collect two complementary measures at the same visit. A panel is a convenience, not a substitute for choosing the right test or confirming an abnormal result.
A fasting Insulin Test may add context when a clinician is evaluating insulin resistance, but insulin is not an accepted stand-alone test for diagnosing prediabetes or type 2 diabetes. Insulin results vary with fasting conditions, timing, medications, and the laboratory method.
A Lipid Panel Test can help assess cardiovascular risk that often overlaps with insulin resistance. A Comprehensive Metabolic Panel Test - CMP includes glucose and markers related to kidney, liver, electrolyte, and protein status. Neither test replaces a standard diabetes screening test.
More testing is not automatically better. C-reactive protein, thyroid tests, vitamin D, broad hormone panels, and stand-alone kidney or liver tests are not universal screening tests for type 2 diabetes risk. They may be appropriate when symptoms, medical history, medicines, or another condition create a specific reason to test. Continuous glucose monitoring also is not currently recommended as a general screening or diagnostic method for people without diabetes.1
Review your family history, prior pregnancy history, medicines, blood pressure, weight trend, waist pattern, activity, sleep, and previous glucose results. A risk assessment can help determine whether testing is due. Record the date, fasting status, units, reference range, and any illness or medicine changes that could affect each result. Ulta's guide to how to read lab results explains why trends and clinical context matter more than an isolated number.
For adults at high risk who have overweight or obesity, the Diabetes Prevention Program used an individualized goal of at least 7% weight loss and at least 150 minutes of moderate physical activity each week. Current ADA guidance recommends a similar initial weight-loss target of at least 5% to 7%. In the original trial, the intensive lifestyle program reduced the rate of type 2 diabetes by 58% over about three years compared with placebo; that is a group result from a clinical trial, not a guarantee for an individual.3
Weight loss is not the only marker of progress, and weight-focused advice may not be appropriate for everyone. Fitness, strength, sleep, blood pressure, food quality, and glucose trends also matter. If you have a history of disordered eating, are pregnant, are underweight, or have a condition that affects nutrition, seek individualized guidance rather than pursuing a calorie or weight target on your own.
A CDC-recognized National Diabetes Prevention Program offers coaching, peer support, and a yearlong structure for building habits. Similar evidence-based programs may be available through health systems, community organizations, employers, or insurers.4
No single diabetes-prevention diet is best for everyone. Evidence supports several patterns, including Mediterranean-style, lower-carbohydrate, and predominantly plant-based approaches, when they emphasize minimally processed foods and match a person's culture, preferences, resources, and medical needs.5
Carbohydrate quality and portion size both matter. Favor vegetables, beans, lentils, intact whole grains, and whole fruit more often than refined grains, sweets, and sugar-sweetened drinks. Pairing carbohydrate foods with fiber, protein, or unsaturated fat can make meals more satisfying and may reduce large post-meal glucose swings.
Build meals around vegetables and other fiber-rich foods, then add a protein source such as fish, poultry, eggs, beans, lentils, tofu, or unsweetened dairy if appropriate. Choose nuts, seeds, avocado, olive oil, and other unsaturated fats more often than foods high in saturated fat. The best proportions depend on energy needs, glucose response, kidney health, allergies, medications, and personal preferences.
Start with a change that is easy to repeat: replace a sugary drink with water or an unsweetened option, add a nonstarchy vegetable to one daily meal, or prepare beans or lentils once a week. For more detail, see The Insulin Resistance Diet: Managing Blood Sugar and Health.
Work toward at least 150 minutes per week of moderate-intensity aerobic activity, spread across at least three days when possible, and add resistance exercise two or more days per week if it is safe for you. A brisk walk, cycling, swimming, dancing, or active household work can count. Breaking up long periods of sitting with brief movement is also useful.
If you are inactive, begin below the target and progress gradually. Stop and seek medical advice for chest pain, fainting, severe breathlessness, or new neurologic symptoms. People with cardiovascular disease, major joint limitations, pregnancy, or other health concerns may need a tailored activity plan.
Short sleep, irregular sleep timing, and untreated sleep disorders are associated with worse glucose regulation. Aim for a consistent sleep opportunity and talk with a clinician if you snore loudly, stop breathing during sleep, awaken gasping, or remain very sleepy during the day. Stress does not single-handedly cause diabetes, but chronic stress can affect sleep, eating, activity, medication use, and glucose-regulating hormones. Useful tools may include scheduled movement, breathing practices, counseling, social connection, or changes to an unsustainable workload.
Smoking increases the risk of type 2 diabetes and cardiovascular disease. If you use tobacco or nicotine, ask about counseling and evidence-based cessation treatment. Alcohol can add calories, disrupt sleep, affect triglycerides, and interact with medicines. If you drink, avoid heavy use and discuss an appropriate limit with a clinician; some people should not drink at all. Sugary alcoholic drinks can also raise glucose quickly.
Blood pressure, cholesterol, triglycerides, sleep apnea, fatty liver disease, and excess weight often cluster with insulin resistance. Treating them can reduce overall cardiovascular risk even when glucose remains below the diabetes range. The pattern is explained further in Metabolic Syndrome Blood Tests and Metabolic Health and Weight-Loss Blood Tests.
Ask whether any prescription or over-the-counter medicine could affect glucose. Do not stop a glucocorticoid, antipsychotic, or other necessary medicine on your own. A clinician can weigh the benefits, risks, dose, alternatives, and monitoring plan.
Choose two or three measures that connect to action, such as weekly activity minutes, sleep consistency, blood pressure, waist or weight trend when appropriate, and periodic laboratory results. Reassess the plan after illness, major weight change, pregnancy, a new medicine, or a result moving toward the diabetes range.
Metformin may be considered for selected adults at particularly high risk, especially younger adults with obesity, higher fasting glucose or A1C, or a history of gestational diabetes. Lifestyle intervention was more effective overall in the original Diabetes Prevention Program, although metformin helped some groups.3 No medicine or supplement should be started solely from an online risk score or one laboratory result. Discuss benefits, adverse effects, contraindications, and monitoring with a qualified clinician.
A history of gestational diabetes raises long-term type 2 diabetes risk. Postpartum testing and ongoing screening every one to three years are generally recommended, even when glucose returned to normal after pregnancy.1 Testing during a current pregnancy follows different criteria and should be coordinated with prenatal care.
People with polycystic ovary syndrome can have increased insulin resistance and diabetes risk regardless of body size. Screening choice and frequency should reflect menstrual and pregnancy history, medicines, symptoms, and other risk factors. Read more about the PCOS and diabetes connection.
Type 2 diabetes can occur in youth, but screening criteria and interpretation differ from routine adult guidance. A pediatric clinician should direct testing, especially when a child has symptoms, rapid weight change, a strong family history, or signs of insulin resistance.
Acute illness, surgery, severe stress, changes in nutrition, and some medicines can temporarily change glucose. Repeat testing after recovery or treatment adjustment may be appropriate. A clinician should interpret results in context rather than labeling a transient elevation as a permanent diagnosis.
| Situation | Typical next step |
|---|---|
| Normal screening result | Repeat at least every 3 years; consider sooner if risk changes. |
| Prediabetes | Test at least yearly and use an effective prevention intervention. |
| Previous gestational diabetes | Ongoing screening every 1 to 3 years after postpartum testing. |
| Result in the diabetes range without clear symptoms | Arrange prompt clinical follow-up and confirm the abnormal result. |
| New symptoms or a major risk change | Seek assessment rather than waiting for the routine interval. |
Intervals are a framework, not a substitute for medical judgment. The type of test may also change. For example, a two-hour oral glucose tolerance test can identify impaired glucose tolerance that fasting glucose or A1C misses, while A1C may be more practical for tracking a longer-term pattern.
Eligible adults who want direct access to testing can review how direct-access lab testing works. Availability and ordering eligibility can vary. Testing should complement, not replace, professional medical care.
Not always. Evidence-based lifestyle changes can substantially reduce or delay type 2 diabetes in many high-risk adults, but genetics, age, health conditions, medicines, and social circumstances also affect risk. Prevention is risk reduction, not a guarantee.
A1C, fasting plasma glucose, and a two-hour 75-gram oral glucose tolerance test are all accepted options for nonpregnant adults. They assess different aspects of glucose regulation and can disagree. The best choice depends on fasting practicality, pregnancy status, symptoms, medical history, and factors that could make A1C unreliable.
No. Fasting insulin can add context in selected evaluations, but there is no universally accepted fasting insulin cutoff that diagnoses insulin resistance, and it is not a diagnostic criterion for prediabetes or diabetes.
Yes. A1C is an average and may not show post-meal elevations that an oral glucose tolerance test detects. It can also be affected by conditions that change red blood cells or hemoglobin. Risk factors and other glucose results still matter.
For high-risk adults with overweight or obesity, an initial loss of about 5% to 7% was an evidence-based goal in diabetes-prevention research and current guidance. More is not automatically better, and weight loss may not be appropriate for everyone. A safe target should reflect your health, medicines, nutritional needs, and history.
It is a well-supported minimum target for many adults and was part of the Diabetes Prevention Program. Adding resistance training and reducing prolonged sitting can provide further benefit. Start at a safe level and build gradually.
No supplement has been shown to reliably replace effective lifestyle intervention or appropriate medical care. Research on individual supplements is mixed, products vary in dose and quality, and some interact with medicines. Routine vitamin D testing or supplementation solely to prevent type 2 diabetes is not supported for everyone.
At least yearly is a common recommendation, with earlier testing when symptoms, pregnancy, medicines, illness, or risk factors change. A clinician may adjust the interval based on how close results are to the diabetes range.
Eligible adults may be able to order certain laboratory tests directly where available. Choose a focused test based on your risk and preparation requirements, then share abnormal, conflicting, or unexpected results with a clinician. Direct access does not replace diagnosis or treatment.
Seek prompt medical advice for a result in the diabetes range, especially with increased thirst, frequent urination, unexplained weight loss, or blurred vision. Vomiting, abdominal pain, deep or rapid breathing, confusion, severe weakness, or loss of consciousness can signal a medical emergency and requires urgent care.
The most useful plan to prevent or delay type 2 diabetes combines appropriate screening with repeatable daily actions. Know your risk, choose the glucose-based test that fits the clinical question, use results as a trend rather than a verdict, and focus on changes that improve overall health. If testing identifies prediabetes, act early with a structured prevention program and a follow-up plan. If results are in the diabetes range, conflict with one another, or occur with symptoms, seek clinical evaluation rather than trying to interpret or treat them alone.
Originally published: May 6, 2024 | Substantively updated: August 27 2026
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