Phentermine

Introduction

Written by Sarah Lewis, PharmD
Medically reviewed by Stan Saji, PharmD, MBA, RPH
Updated on 07/24/2025

Phentermine is a generic medication prescribed for weight loss in certain adults. The brand-name versions of this drug are Adipex-P and Lomaira. The cost of phentermine with or without insurance can depend on several factors. It might be lowered by using a coupon.

Read on to learn about phentermine and its cost. You’ll also find coupons and suggestions for ways to save on your prescription. If you’d like more information about phentermine, including its uses, refer to this overview article.

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Cost of phentermine

Like other medications, the cost of phentermine can vary. Certain factors may affect its price, such as:

• your insurance plan, if you have coverage
• the pharmacy you use
• your location

To find out how much phentermine costs, ask your doctor, pharmacist, or insurance provider. They may be able to suggest ways to save money on your prescription, including those described in this article. To find out what you’d pay using savings coupons, read the “Coupons for phentermine” section.

Coupons for phentermine

Prescription drug coupons can help you save money by lowering the cost of phentermine. The Optum Perks coupons above can provide significant savings on your prescription costs.

Note: Optum Perks coupons cannot be used with any insurance copays or benefits.

Available app for coupons

To make finding and using these coupons easier, you can download the Optum Perks app. To learn more about this prescription discount app, see this article.

Insurance and other considerations for phentermine

Here’s a list of things to consider about the cost of prescription drugs:

• Prior authorization: If you have prescription drug insurance, your insurance company may require prior authorization before it covers the cost of phentermine. In this case, your doctor will communicate with your insurance company regarding your prescription for phentermine. The insurance company will decide whether to cover the medication. If a drug requires prior authorization and you begin taking it without this, you may have to pay the full price of the drug.
• A 3-month supply: If you’re taking phentermine long term, your doctor may suggest a 90-day supply of the medication. This will have to be approved by your insurance company. Getting a 90-day supply could help lower the drug’s cost. It could also save you time having to make trips to your pharmacy.
• Savings accounts: If you’re eligible for a health savings account (HSA) or a flexible spending account (FSA), you can likely use funds from these accounts to pay for your prescription or over-the-counter (OTC) medications. HSA and FSA plans help people save money by using pretax dollars to pay for eligible healthcare expenses, such as prescription and OTC drugs. To learn more about whether you’re eligible for these savings accounts and how to use them, talk with your insurance provider or employer.

If you have questions about any of these considerations, ask your doctor or pharmacist. Or contact your insurance company and talk with a representative.

If you don’t have a health insurance plan, let your doctor or pharmacist know. They may suggest online pharmacy options you could use. You can also ask them about ways to obtain health insurance coverage.

Common questions about phentermine and cost

Here are some common questions about phentermine and their answers. 

How long can phentermine be used for?

Phentermine is only approved for short-term use of a few weeks, and usually less than 3 months. Doctors may prescribe it intermittently, meaning you can start taking it again after a short break. It’s generally prescribed along with exercise and a balanced diet.

According to some 2021 research, many people see reductions of around 4.5 kilograms (kg) after 3 months of treatment with 15 grams (g) of phentermine and reductions of 5.8 kg after treatment with a 30-g dose.

Is there an over-the-counter (OTC) form of phentermine?

Phentermine is not available OTC, and there are no OTC versions of the medication. Phentermine is considered a controlled substance due to its potential for dependence and misuse.

When taking phentermine for weight loss, how much does it cost without insurance?

Insurance coverage is a major factor that affects the cost of prescription drugs. In general, prescriptions will cost more without an insurance plan compared to paying through one.

Phentermine is a generic drug. Generics are usually less expensive than brand-name versions. If you’re paying out of pocket, generics will probably save you money over the brand-name drugs.

Also, if you’re paying for phentermine without insurance, you may be able to find online coupons to help with the cost. See the “Coupons for phentermine” section for more information.

Why are costs different for brand-name drugs vs. generic drugs?

Brand-name drugs can be expensive because of the studies needed to test how safe and effective they are.

Makers of a brand-name drug can sell their drug for up to 20 years. When the patent for a brand-name drug expires, other drugmakers can make and sell generic versions. A generic medication is an identical copy of the active drug in a brand-name medication. An active drug is the ingredient that makes medication work.

This competition may help keep the costs of generic medications lower. Also, generic medications contain the same active drugs as brand-name medications. So they don’t require the same testing, which can be costly.

If you’d like to know more about the cost differences between brand-name and generic drugs, talk with your doctor.

Generics vs. brand-names

Phentermine is a generic medication. The brand-name versions of this drug are Adipex-P and Lomaira.

A generic medication is an identical copy of the active drug in a brand-name medication. An active drug is the ingredient that makes a medication work. Generics usually cost less than brand-name drugs. And they’re considered as safe and effective as the brand-name versions.

If your doctor has prescribed phentermine but you’re interested in taking Adipex-P or Lomaira, let them know. They may prefer one medication over the other. Also, check whether your insurance plan covers only one version of the drug.

To learn how the cost of phentermine compares with its brand-name versions, talk with your doctor or pharmacist. You could also contact your insurance company. 

Resources

• Food and Drug Administration. (2025). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Márquez-Cruz M, et al. (2021). Three- and six-month efficacy and safety of phentermine in a Mexican obese population. https://europepmc.org/article/med/34236303
• Phentermine hydrochloride capsules USP, for oral use CIV. (2024). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/a0439c85-5ede-4e02-aed2-47debd2c8eb2/spl-doc
• Phentermine hydrochloride tablets, for oral use, CIV. (2024). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/c5d60a6d-2410-4a3c-88e1-a6126b56cf6a/spl-doc

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.