BMI — body mass index — is the primary gatekeeper for GLP-1 weight loss prescriptions. It's a blunt tool, and plenty of doctors will tell you it doesn't capture the full picture of someone's health. But it's the metric the FDA uses, insurers rely on, and clinics screen with. Knowing where you stand and what the thresholds mean is the first step toward getting treatment.
The FDA Criteria
For GLP-1 medications approved specifically for weight loss — Wegovy and Zepbound — the FDA-approved criteria are:
- BMI of 30 or higher (classified as obesity), or
- BMI of 27 or higher with at least one weight-related health condition
Those qualifying conditions include type 2 diabetes, high blood pressure, high cholesterol, obstructive sleep apnea, and cardiovascular disease, among others. In practice, this second category captures a lot of people. You don't need to be severely obese to qualify — a 5'8" person weighing 180 pounds has a BMI just over 27, and if they also have high blood pressure, they meet the criteria.
Not sure where you fall? Our BMI calculator gives you a quick answer.
What Clinics Actually Look At
FDA criteria set the floor, but clinics use their own judgment too. Most weight loss providers follow the FDA guidelines closely, but some are more flexible and others more conservative. A handful of clinics — particularly telehealth providers — will prescribe at lower BMIs if the patient has significant comorbidities and has failed other weight loss approaches. Others stick rigidly to the numbers.
Your initial consultation will typically include a full medical evaluation, not just a BMI check. Providers consider your weight history, family history of obesity, metabolic markers from blood work, and how your weight is affecting your overall health and quality of life. BMI gets you in the door, but the clinical assessment determines the treatment plan.
BMI of 27-29: The Gray Zone
If your BMI falls between 27 and 29.9, you're in territory where the qualifying comorbidity matters. This is where documentation helps. If you have a formal diagnosis of hypertension, pre-diabetes, dyslipidemia, or sleep apnea in your medical records, getting a prescription is straightforward. If those conditions haven't been formally diagnosed, your doctor might want to run tests first.
For insurance coverage specifically, a documented comorbidity is usually required for prior authorization at this BMI range. Your provider's office should know what your insurer needs and can help build the case. This is one reason working with an experienced weight loss clinic matters — they handle these authorizations regularly.
What If Your BMI Is Below 27?
The honest answer: most providers won't prescribe a GLP-1 for weight loss at a BMI under 27. The medications weren't studied in that population, and the risk-benefit calculation changes when there's less excess weight to lose. Side effects like nausea, muscle loss, and nutritional deficiency become proportionally more concerning.
If you're close to the threshold and frustrated, there are a few things to consider. First, BMI fluctuates — your weight at the morning appointment may be different from your weight after a normal day of eating and hydrating. Second, if you have metabolic issues that don't show up in BMI (visceral fat, insulin resistance), bring those lab results to the conversation. Some providers will weigh these factors.
But if you're genuinely at a healthy weight and want GLP-1s for cosmetic reasons, most responsible providers will decline. These are serious medications with real side effects, and they're designed for people with clinically meaningful excess weight.
The Limitations of BMI
BMI doesn't distinguish between muscle and fat. A muscular person can have a "high" BMI while being perfectly healthy. It also doesn't account for where you carry your weight — abdominal fat is far more dangerous than fat distributed elsewhere. Some doctors supplement BMI with waist circumference measurements or body composition analysis for a fuller picture.
Despite its shortcomings, BMI isn't going away as a prescribing criterion anytime soon. It's simple, standardized, and universally understood. Organizations like the Obesity Action Coalition offer helpful resources for understanding how BMI and other health markers factor into treatment eligibility. The best approach is to know your number, understand the thresholds, and come to your appointment prepared to discuss your full health picture. Find a GLP-1 provider who takes a thorough approach to evaluation — not just a number on a scale.