Phentermine

The most common side effects are dry mouth, insomnia (especially if taken too late in the day), increased heart rate, jitteriness or restlessness, and constipation. These are typically mild and tend to improve as your body adjusts. Because phentermine is a stimulant, it can raise blood pressure and heart rate — which is why PEAK monitors these metrics at every follow-up visit. Taking phentermine in the morning helps minimize sleep disruption.

Phentermine is FDA-approved for short-term use up to 12 weeks. At PEAK, your clinician will discuss the treatment timeline during your consultation and plan for what comes next — whether that's transitioning to a GLP-1 medication, continuing with behavioral and nutritional support, or adjusting the approach based on your response.

In some cases, yes. Combination therapy — using phentermine alongside a GLP-1 like Wegovy or Zepbound — can be clinically appropriate when one medication alone isn't producing sufficient results. The two medications work through completely different mechanisms (appetite suppression via norepinephrine vs. GLP-1 receptor activation), so they can complement each other. Your PEAK clinician will evaluate whether this approach is safe and appropriate for your situation.

Phentermine and GLP-1 medications work through entirely different mechanisms and produce different levels of weight loss. GLP-1 medications (15–22.5% body weight loss) are significantly more effective than phentermine (5–7%) over longer treatment courses. However, phentermine is oral (no injections), easier to access as a generic option, and covered by many insurance plans. Some patients start with phentermine and transition to GLP-1s. Others use both together. Read the full comparison.

Many commercial plans cover phentermine, and generic options can reduce out-of-pocket costs. PEAK accepts Anthem, Cigna, Aetna, UnitedHealthcare, Sentara, and TRICARE commercial plans, and does not accept Medicare or Medicaid plans. Visit pricing is $199 for the initial appointment, $135 for follow-up visits, and $75 for dietitian visits. View insurance and pricing details.

Phentermine is classified as a Schedule IV controlled substance, meaning it has a low but recognized potential for dependence. In practice, physical dependence at prescribed doses is rare. However, because it is a stimulant, it is not recommended for patients with a history of substance abuse. PEAK prescribes phentermine with appropriate clinical oversight, scheduled follow-up visits, and a clear treatment timeline.