Adult BMI Categories

For adults age 20 and older, BMI falls into these standard categories:

Obesity is sometimes divided further into classes to reflect increasing health risk: class 1 (30.0–34.9), class 2 (35.0–39.9), and class 3 (40.0 or greater).

BMI and Weight-Loss Treatment Eligibility

BMI is often discussed in the context of weight-loss treatment, but it is important to be clear about what it can and cannot do.

BMI and GLP-1 Medications

GLP-1 medications such as semaglutide and tirzepatideare often part of weight-management conversations. BMI may come up during that discussion as one input, but there is no single BMI number that guarantees eligibility for any medication. A licensed provider weighs your BMI alongside your complete health picture — conditions, medications, history, and goals — before deciding whether treatment is appropriate. Learn more on our GLP-1 treatments overview.

Limitations of BMI

BMI is useful precisely because it is simple, but that simplicity is also its main limitation. It does not distinguish muscle from fat or account for where fat is stored. It can be misleading for:

• Athletes and people with high muscle mass — muscle is denser than fat, so BMI can overestimate body fat.
• Older adults — who may lose muscle, so BMI can underestimate body fat.
• Pregnant people — standard adult BMI ranges do not apply.
• Certain ethnic groups — health risk can occur at different BMI thresholds.
• Children and teens — who are assessed using age- and sex-specific percentiles instead.

BMI vs Body Fat Percentage

BMI and body fat percentage answer different questions. BMI is a quick height-to-weight ratio; body fat percentage measures the proportion of your weight that is fat, often via methods like skinfold calipers, bioelectrical impedance, or DEXA scans. Body fat percentage can be more precise for individuals, but it usually requires equipment or a clinical setting. For a fast, free screening estimate, BMI remains a practical first step — just remember its limits.

When to Talk to a Healthcare Provider

Consider speaking with a provider if your BMI is outside the healthy range, if you have conditions affected by weight, or if you are thinking about a weight-loss treatment. A provider can interpret your BMI in context and give guidance tailored to you. If you would like to start that conversation, our medical review team reviews each request individually.

References

• Centers for Disease Control and Prevention (CDC). Adult BMI Calculator and Adult BMI Categories.
• Centers for Disease Control and Prevention (CDC). Child and Teen BMI — percentile-based interpretation.
• National Heart, Lung, and Blood Institute (NHLBI). Classification of overweight and obesity by BMI.
• U.S. Food & Drug Administration (FDA). Compounding and the FDA: Questions and Answers.

BMI results are estimates for educational purposes only. This calculator does not diagnose a medical condition and does not determine whether you qualify for weight-loss medication. A licensed provider must review your health history before any treatment decision.