Sexual Side Effects

Phentermine and Sexual Side Effects

Changes in libido and impotence are not the most talked-about phentermine side effects, but with over 17% of users reporting phentermine sexual side effects, these reactions are worth discussing ( 1 ).

Some people experience increased libido, while others have no sex drive at all or even sexual dysfunction.

Does Phentermine Affect Sex Drive?

A young couple frustrated about phentermine sex drive changes
Almost 1 in 5 patients experience phentermine sex drive changes

Yes, phentermine can either increase or decrease users’ interest in sex. The medication can also cause sexual dysfunction, which leads to further problems with patients’ sex lives.

Interestingly, common phentermine sex-drive changes differ between genders. While men tend to suffer from lower sex drive, women are more likely to report increased libido while taking phentermine ( 2 ).

Sexual Side Effects of Phentermine

The FDA’s list of common phentermine side effects includes two sex-related reactions ( 3 ):

  • Sexual impotence
  • Change in sexual desire

These and other, unlisted phentermine sexual side effects occur in both men and women.

Successful sexual arousal and performance is dependent on a delicate balance of central nervous system (CNS) signals, so it is not surprising that CNS stimulants like phentermine often affect this process – either for better or worse.

Thankfully, user reports suggest that phentermine sexual side effects usually resolve in 1-2 weeks, or as soon as the body adjusts to the new medication.

Consult a doctor if phentermine sexual side effects get worse or don’t go away. There are a variety of medications that can help, as can adjusting your dose or schedule.

The most common phentermine sexual side effects include:

1. Sexual Dysfunction or Impotence

Phentermine promotes weight loss by stimulating the central nervous system.

The hormonal changes associated with this simulated “fight or flight” reaction suppresses appetite and boost energy, which promote weight loss. However, the same hormones also signal the body to divert blood flow away from less-essential areas, such as the digestive system and reproductive organs ( 4 ). As a result, some phentermine patients experience sexual dysfunction related to hormonal changes or decreased blood flow to the genital region.

In men, this usually presents as erectile dysfunction, while women may experience dryness, pain or trouble orgasming during sex.

Erectile Dysfunction

A small percentage of male phentermine users experience erectile dysfunction (ED).

Getting an erection requires intricate cooperation between the brain, blood vessels, nerves and hormones. Unfortunately, stimulant medications like phentermine can make it difficult to get aroused or achieve an erection because they disrupt this delicate balance.

Decreased blood flow to the penis and stimulant-related mood changes can both make it harder for men to get and maintain an erection while taking phentermine.

Sexual Dysfunction

While impotence is not as much of an issue for women, female phentermine users may experience sexual dysfunction in the form of difficulties getting (or staying) aroused, trouble orgasming or pain during intercourse ( 5 ).

These reactions can occur for a wide variety of reasons but, similar to male patients, stimulant-related sexual dysfunction in women often stems from decreased blood flow to the clitoris and/or mood changes.

2. Changes in Sex Drive

Phentermine can either increase or decrease sex drive.

Some patients, typically men, struggle with decreased interest in sex while taking phentermine. This is likely related to the fact that stimulants like phentermine increase levels of the neurotransmitter, serotonin. Research indicates that higher levels of this feel-good chemical counteract proerectile neurotransmitters, thereby inhibiting erections, decreasing interest in sex and making it harder to achieve orgasm ( 6 ). The end result is that phentermine decreases libido in some users.

Other patients, however, experience the opposite effect: that phentermine and increased libido come hand-in-hand. This reaction is most commonly seen in female patients. Heightened sex drive is most-likely related to hormonal changes, as well as disruption of the delicate balance between the sympathetic (stress) and parasympathetic (rest) nervous systems. In fact, research suggests that increased sympathetic nervous system activation, as occurs with phentermine, may boost sexual response in women ( 7 ).

3. Other Sexual Side Effects

In addition to phentermine sex-drive changes and erectile dysfunction, male phentermine users also report penis and scrotum shrinkage, increased ejaculation, and not feeling satisfied after sex as reactions to this medication. Some men also describe increased frequency and decreased volume of urination while taking phentermine.

Some women experience menstrual changes while taking this medication.

Click here to read more about phentermine and your period.

How to Cope with Phentermine Sexual Side Effects

woman doing yoga
Exercise may help alleviate phentermine sexual side effects

If your phentermine sexual side effects are mild or temporary, consider an at-home solution to alleviate some of the symptoms. Proper nourishment, regular activity and the right mentality are a great place to start.

1. Eat Right

Some patients find that making nutritious dietary choices and taking care of themselves helps restore their interest in sex, even before the weight starts coming off. Choose plenty of fruits, vegetables, lean proteins, whole (fiber-rich) grains and healthy fats to fuel your weight loss.

2. Get Your Blood Pumping

Exercise is good for weight loss, and it may also reduce phentermine sexual side effects. Lower body exercises that activate the glutes, upper leg muscles and increase blood flow to the pelvic region can help alleviate sexual dysfunction/impotence or even increase sex drive ( 8 ).

A brisk walk or hike, leisurely bike ride or some relaxing yoga moves are a great place to start.

3. Play the Mental Game

We spend a lot of time focused on things we can do to help the body get ready for sex, but the mind is important too!

Practice meditation or other relaxing activities to reduce stress and allow yourself to be fully present in the bedroom. More, work on loving and accepting yourself at any size since the better you feel, the more you (and your partner!) can enjoy sex.

Talk to a doctor if any phentermine sexual side effect is bothering you, getting worse or interfering with your life or relationship. He or she can work with you to determine the cause of the problem and help you develop a plan to help get things back to normal ASAP.

Back to All Phentermine Side Effects

  1. Members of “Losing Weight with Phentermine” Support Group on Facebook & Forum. (2019, March 13). [User Report of Common Phentermine Side Effects]. Unpublished raw data.
  2. Forum. (2018, November 23).
  3. U.S. Food and Drug Administration. (2012). Adipex-P (phentermine hydrochloride) capsules label [Brochure].
  4. Sinfield, J., & Gans, S. (2018, October 25). Adderall Side Effects in Men.
  5. Mayo Clinic Staff. (2018, September 06). Female sexual dysfunction.
  6. Goldstein, I. (2003, February 7). Boston University Medical Campus – Sexual Medicine.
  7. Meston, C. M. (2000). Sympathetic nervous system activity and female sexual arousal [Abstract]. The American Journal of Cardiology, 86(2), 30-34. doi:10.1016/s0002-9149(00)00889-4
  8. Bouchez, C. (2005, March 25). Better Sex: What’s Weight Got to Do with It?