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Phen Diet Pills Side Effects

By Linda Tarr Kent ; Updated July 18, 2017

Phen diet pills contain a substance called phentermine. Phen works by decreasing your appetite, according to PubMed Health. You need to be careful with phen diet pills because they can be habit forming. Most people take such pills for three to six weeks. To lessen side effects, take these diet pills with meals. Also take them under a doctor’s supervision.

Less Serious Side Effects

You need to consult a doctor if you have certain symptoms that are persistent or severe when using phen diet pills, according to PubMed Health. These include a dry mouth, diarrhea, an unpleasant taste, vomiting and constipation. You also may experience itching, an anxious feeling or nervousness, reports


Phen can impair your reactions and your thinking, according to This means you need to avoid drinking alcohol along with phen, and also need to take care if driving or doing another activity that requires you to be alert.

Heart Issues

Phen can cause increased blood pressure, heart palpitations or chest pain. If you experience any of these symptoms you need to get immediate medical attention, according to PubMed Health.

Other Issues That Require Medical Attention

You may experience restlessness, dizziness, insomnia, tremors or leg and ankle swelling when taking phen diet pills. Contact your doctor immediately if you have any of these effects, recommends PubMed Health.

Shortness of Breath

If you feel shortness of breath or have difficulty doing exercises you’ve previously been able to perform notify your doctor right away, advise the experts at PubMed Health.

Life Threatening Issues

Phen diet pills in the past were combined with fenfluramine to create the fen-phen pill. These pills were popular in the 1980s and 1990s and are associated with heart valve trouble, reports Christine Gorman of TIME magazine in the July 21, 1997 article, “Danger in the Diet Pills?” The Federal Drug Administration no longer allows fen-phen to be marketed in the United States. warns that taking phen pills along with fenfluramine or dexfenfluramine can lead to a rare and fatal lung disorder known as pulmonary hypertension.

Phen can have serious and life threatening effects if you take it along with MAO inhibitors. These include isocarboxazid, phenelzine, rasagiline, selegiline and tranylcypromine. If you have taken these drugs within 14 days they may not be cleared from your system. Avoid phen until they are eliminated from your body, advise the experts at

Pregnancy Concern

Avoid phen if you are pregnant or nursing, as it is not known whether this diet pill will harm an unborn baby or infant, according to

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