Everything you need to know about Phentermine in 2026 — what it is, how it's used, dosages, who should avoid it, and how much it costs.
Phentermine is one of the oldest and most commonly prescribed weight-loss medications in the United States. It's been helping patients lose weight since the 1950s, and it remains a popular option in 2026 because it's effective, well-studied, and affordable.
This guide covers everything you need to know — from what Phentermine is and how it's used to dosage, safety, and cost.
Phentermine (sold under brand names Adipex-P, Lomaira, and formerly Ionamin) is a prescription medication in the sympathomimetic amine class. It works as an appetite suppressant by affecting chemicals in the brain that control hunger. For a detailed explanation of how it works at the molecular level, see our article on Phentermine's mechanism of action.
Key facts:
Phentermine is FDA-approved as a short-term (up to 12 weeks) adjunct treatment for obesity. That means it's meant to be used alongside a reduced-calorie diet, exercise, and behavioral changes — not as a standalone solution.
To qualify, you typically need:
Some doctors prescribe Phentermine for longer than 12 weeks based on clinical judgment, though this is considered off-label use.
Phentermine is also available as part of the combination medication Qsymia (Phentermine/Topiramate extended-release), which is FDA-approved for longer-term use.
Phentermine comes in several forms and strengths:
The most common regimen is 37.5 mg once daily, taken in the morning before breakfast or 1 to 2 hours after breakfast. Taking it early helps prevent insomnia — one of the most common side effects.
An alternative is 8 mg three times daily, taken 30 minutes before each meal. This lower-dose option (the Lomaira approach) may cause fewer side effects for some patients.
Important instructions:
Phentermine is not safe for everyone. It's contraindicated in patients with:
Phentermine is also not recommended for patients over 65 or for children under 16. If you have any of these conditions, talk to your doctor about alternative weight-loss options.
One of the biggest advantages of Phentermine is its price. Because generic versions are widely available, it's one of the most affordable prescription weight-loss medications:
Coverage for weight-loss medications varies widely:
Even without insurance, Phentermine is affordable with the right discount. Check our complete savings guide for coupon cards, discount programs, and tips on getting the lowest price.
Phentermine remains a proven, affordable, and widely available option for short-term weight loss when combined with diet and exercise. It's not right for everyone — especially those with heart conditions, a history of drug abuse, or who are pregnant — but for eligible patients, it can be an effective tool.
If you have a prescription and need to find Phentermine at a pharmacy near you, Medfinder can help you check stock quickly and easily.
You focus on staying healthy. We'll handle the rest.
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