Are Diet Pills With Phentermine Dangerous?

Erin Coleman, R.D., L.D.
Diet pill

Phentermine is the generic name for a prescription weight loss product that helps suppress your appetite. Brand names of drugs containing phentermine include Lomaira, Lonamin, Qsymia and Adipex. These products are used to help speed up weight loss in people who are obese and are available by prescription only. The dosage of phentermine in each brand name product varies by product.

Is Phentermine Dangerous?

Phentermine is often effective for weight loss, but it can be dangerous for some people due to the possibility of serious (even life-threatening) side effects. Phentermine can be dangerous for people who are allergic to the product, and it isn't recommended for long-term use. It can interact with certain medications, so always chat with your doctor before agreeing to try phentermine to shed pounds.

Possible Side Effects

Side effects of phentermine to watch out for include:

  • Allergic reactions (itching, hives, chest tightness trouble breathing, mouth tingling and swelling)
  • Diarrhea
  • Constipation
  • Vomiting
  • Cramps
  • Unpleasant taste
  • Dry mouth
  • Nervousness
  • Heart palpitations
  • Dizziness
  • Restlessness
  • Increased blood pressure
  • Tremors
  • Shortness of breath
  • Trouble breathing
  • Chest pain
  • Fainting
  • Insomnia
  • Chest pain
  • Swelling
  • Drowsiness
  • Headache
  • Changes in sex drive
  • Impotence
  • Confusion
  • Irritability

When to Avoid Phentermine

There are several population groups who should avoid taking phentermine due to safety concerns. MedlinePlus cautions older adults (65 years or older) shouldn't take phentermine because it's not as safe as other weight loss medications for this age group.

Mayo Clinic warns to avoid phentermine if you have high blood pressure, heart disease, glaucoma, thyroid disease, are pregnant, are breastfeeding, or you may become pregnant (phentermine can cause problems in a developing baby). Avoid this product if you drink alcohol, warns PubMed Health. Likewise, since phentermine can cause changes in blood sugar levels, talk with your doctor if you have diabetes.

Other Reasons to Be Cautious

In addition to unpleasant and dangerous potential side effects of phentermine, you may want use it as a last resort for several other reasons. PubMed Health says phentermine is habit-forming, meaning you can get addicted to it. For this reason, it's only safe to take the medicine for short time periods and slowly wean off of it after you've slimmed down.

Cigna cautions to avoid taking phentermine if you've taken certain medications (MAO inhibitors) within the past two weeks including linezolid, rasagiline, isocarboxazid, phenelzine, tranylcypromine, and selegiline.

Weighing Pros and Cons

Because there are so many potential dangerous side effects associated with taking phentermine, always chat with your doctor to determine if choosing this type of weight loss product is really worth your while. Pros include rapid weight loss due to decreases in appetite, which is beneficial if you're obese and want to lower obesity-related health risks (like heart disease, diabetes and cancer). However, check in with your doctor to determine if phentermine is safe enough for you and report any side effects immediately if you're experiencing them.

Err on the Safe Side

When trying to shed pounds, phentermine should be your last line of defense due to possible life-threatening side effects that can occur. This product is really only for people who have lots of pounds to lose who have already tried diet and exercise without success. Your best bet is to try other weight loss alternatives first, and use phentermine as a last resort.

Are Diet Pills With Phentermine Dangerous?