About Phentermine

What is Phentermine

Phentermine is a stimulant similar to an amphetamine. It acts as an appetite suppressant by affecting the central nervous system.

Phentermine is used together with diet and exercise to treat obesity (overweight) in people with risk factors such as high blood pressure, high cholesterol, or diabetes.

Phentermine may also be used for purposes not listed in this medication guide.

Important Information


Do not use phentermine if you are pregnant or breast-feeding a baby.

You should not take phentermine if you have a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke), severe or uncontrolled high blood pressure, overactive thyroid, glaucoma, a history of pulmonary hypertension, if you are in an agitated state, or if you have a history of drug or alcohol abuse.

Do not use phentermine if you have taken an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.

You should not take phentermine if you are allergic to it, or if you have:

  • a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke);

  • a history of pulmonary hypertension;

  • severe or uncontrolled high blood pressure;

  • overactive thyroid;

  • glaucoma;

  • if you are pregnant or breast-feeding;

  • if you are in an agitated state;

  • if you have a history of drug or alcohol abuse; or

  • if you are allergic to other diet pills, amphetamines, stimulants, or cold medications.

Taking phentermine together with other diet medications such as fenfluramine (Phen-Fen) or dexfenfluramine (Redux) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take this medicine with any other diet medications without your doctor's advice.

To make sure you phentermine is safe for you, tell your doctor if you have:

  • high blood pressure;

  • diabetes;

  • kidney disease;

  • a thyroid disorder; or

  • if you are allergic to aspirin or to yellow food dye (FD & C Yellow No. 5, or tartrazine).

Phentermine may be habit forming. Never share phentermine with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.

Get emergency medical help if you have any of these signs of an allergic reaction to phentermine: hives; wheezing, chest tightness, trouble breathing; swelling of your face, lips, tongue, or throat.