Phentermine FAQs

What are the side effects of phentermine?

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As with all medications, people who take phentermine may suffer some side effects. You can find out more information in our phentermine side effects section, but this list below gives a comprehensive guide to the types of side effects you may suffer from. 

Common phentermine side effects include:

  • Dry mouth
  • Unpleasant taste in mouth
  • Constipation
  • Diarrhea
  • Headaches
  • Restlessness
  • Insomnia
  • Irritability
  • Tiredness
  • Low mood
  • Feelings of nervousness
  • Impotence
  • Changes in libido

Less common side effects of phentermine include:

  • Blurred vision
  • Dizziness
  • Confusion
  • Fatigue
  • Irregular heartbeat
  • Stomach pain
  • Nausea
  • Feelings of depression

Other possible side effects of phentermine may be more serious. If you experience any of the following, contact your doctor immediately:

  • Suspected allergic reaction (skin rash, itching, facial swelling, short breaths, tight chest)
  • Difficulty breathing
  • Swelling of the mouth, legs or feet
  • Racing heart beat
  • Fainting
  • Chest pains
  • Uncharacteristic behavior
  • Psychosis

If you are uncomfortable with the prospect of these phentermine side effects, you might want to consider using an alternative to phentermine. Here at, we officially recommend the weight loss supplement Phen Caps. Like phentermine, Phen Caps help you to lose weight by suppressing appetite and boosting energy levels, however they have no side effects. If you want to learn more about Phen Caps, please click here.

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