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Can Phentermine Cause Hair Loss?

Knox Beasley, MD

Reviewed by Knox Beasley, MD

Written by Rachel Sacks

Published 12/04/2022

Updated 04/03/2024

If you take an appetite suppressant like phentermine, you’re probably hoping it’ll just reverse or prevent weight gain, not cause you to lose a full head of hair (and maybe body hair too). So is phentermine hair loss a thing — can phentermine cause hair loss? Or is your hair falling out for another reason?

Any medication can have side effects, and the weight loss medication phentermine is no exception. But whether phentermine causes hair loss is a bit more complex.

You’re not the first person to wonder, Does phentermine make your hair fall out? We’ll definitely answer this below, but the explanation isn’t exactly black and white.

We’ll get to the bottom of this weight loss drug’s connection to hair loss and go over treatment options for restoring your luscious locks. We’ll also answer all your lingering questions from that Google search of “phentermine side effects hair loss.”

Though it’s not listed as a side effect, some people who take the medication report phentermine hair loss. If you take phentermine and lose your appetite, you may not be getting all the nutrients needed for hair growth.

Vitamins and minerals play a vital role in the hair growth cycle and cell turnover. When these things go haywire, hair loss can occur.

Being deficient in certain vitamins and minerals may cause non-scarring alopecia (a type of hair loss). This includes:

  • B vitamins (such as biotin, folate and vitamin B12)

  • Vitamin D

  • Vitamin E

  • Iron

  • Zinc

Most people get enough of these vitamins and minerals from food. But taking an appetite suppressant could mean eating less food overall — and as a result, consuming fewer nutrients.

Why Does Phentermine Cause Hair Loss?

Phentermine hair loss may be due to losing your appetite to the point where you’re not getting enough hair health-boosting nutrients, a condition called acute telogen effluvium.

Telogen effluvium means you’re experiencing excessive shedding of your hair.

To understand the reason behind phentermine hair loss and telogen effluvium, it’s helpful to know the three phases of hair growth.

During the anagen phase, hair grows. In the catagen phase, it stops growing. Then in the telogen phase, your hair rests — in other words, it just chills where it is.

If the telogen phase is shortened for any reason, hair releases from its follicles sooner than it normally would. As a result, you might see an increase in hair shedding and loss.

Things like nutritional deficiencies can shorten the telogen phase. And as noted, folks taking phentermine might not be getting enough nutrients from food.

Will My Hair Grow Back After I Stop Taking Phentermine?

Is hair loss from phentermine permanent? Telogen effluvium is a type of temporary hair loss, so phentermine hair loss most likely won’t be permanent.

When you stop taking the medication or focus on eating more nutrient-dense foods, you’ll probably start shedding less and see improvements in hair growth.

If what you’re experiencing is male pattern baldness (androgenetic alopecia), your hair loss could become permanent — that is, if you don’t act quickly. Learn more in our guide to male pattern baldness.

hair loss treatment

balding can be optional

To make a full connection between phentermine and hair loss, let’s back up a minute and explain what phentermine is.

Phentermine is in a class of amphetamine-like drugs called anorectics. This weight loss medication is prescribed to people already attempting to lose body weight through healthy nutrition and exercise.

For those already implementing healthy eating habits, phentermine can help speed up the weight loss process by decreasing their appetite.

While phentermine may not lead to rapid weight loss, it’s effective at helping some individuals reduce their body mass.

This medication is available in tablets and extended-release capsules. Bear in mind it’s not intended for long-term use and is usually prescribed for three to six weeks.

Common Side Effects of Phentermine

Is phentermine hair loss a side effect? As noted, the drug label doesn’t list hair loss as a potential side effect.

The most common adverse effects associated with taking this medication for weight loss are generally benign (not a cause for serious concern).

Phentermine side effects can include:

  • Vomiting

  • Constipation

  • Diarrhea

  • Dry mouth

  • Unpleasant taste in your mouth

There are some more severe adverse effects to look out for as well. They include high blood pressure, heart palpitations, tremors, insomnia, shortness of breath, chest pain and swelling of the legs.

If you notice any of these symptoms, seek medical attention as soon as possible.

Phentermine Drug Interactions and Considerations

Before you start taking this weight loss medication, alert your healthcare provider about previous allergic reactions you’ve had to medications or any medical conditions you have. That way, they can make sure you don’t have a poor reaction to phentermine or face a potential drug interaction.

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You’re at a crossroads: You want to reach your weight loss goals and keep a full head of hair. The good news is you can have both.

If you’re taking phentermine and notice excessive hair loss or hair thinning, the first thing to do is seek medical advice from your healthcare provider.

Anytime you’re on medication and notice weird symptoms, it’s vital to bring them up. That way, your provider can keep an eye on them and advise you on what to do.

Here are some options that might help with phentermine hair loss, from lifestyle changes to hair loss treatments.

Eat More Hair-Growth Foods

As mentioned, it’s likely not the phentermine itself causing hair loss. What could be happening is that the medication is reducing your appetite to the point of a nutrient deficiency that causes hair to fall out faster than normal.

So how do you reverse phentermine hair loss? One way is to consume more nutrient-rich foods that support hair growth.

Zinc and iron are two essential minerals for healthy hair growth. Eating crab, cashews and oatmeal can help you get more zinc. For iron, try to eat more spinach, lean meats and seafood or take an iron supplement.

Biotin is another nutrient needed for hair growth. It’s found in foods like bananas, eggs and milk.

But if you don’t get enough of this B vitamin through balanced eating, you could take the biotin gummies from Hims. It also contains vitamin D, which, as mentioned above, is necessary for hair health.

Try Hair Loss Medication

Another option is the non-prescription hair regrowth medication minoxidil. Available in liquid or foam formulas, this topical treatment is FDA-approved to treat hair loss.

Minoxidil stimulates hair follicles to enter the growth phase — aka the anagen phase. Plus, it boosts blood flow to the scalp, bringing nutrients to your hair follicles and stimulating growth.

There’s also finasteride, which can be taken orally in tablet form or applied topically. Finasteride lowers DHT (short for dihydrotestosterone), a hormone that can cause hair loss when there’s too much of it in your body.

Your best bet might be to combine these two science-backed medications with a two-in-one treatment like our topical finasteride & minoxidil spray.

Add a Hair Loss Shampoo to Your Routine

Another easy thing you can do is to stick a hair loss shampoo in your shower. This is a good option to use alongside one of the above suggestions.

The thickening shampoo from Hims contains saw palmetto, a natural ingredient thought to help with hair loss by blocking DHT.

Hair loss treatments, delivered

When you take a medication like phentermine, the goal is weight loss, not hair loss.

So then why does phentermine cause hair loss? Here’s what we know:

  • Phentermine is a weight loss medication that suppresses appetite. It’s usually prescribed alongside a healthy eating plan and exercise routine.

  • If you notice hair loss after you start taking phentermine, it might be because you’re not getting enough of certain nutrients — and a nutrient deficiency could lead to hair loss.

  • This type of hair loss, known as telogen effluvium, tends to be reversible with lifestyle changes, like eating more nutritious food rich in hair-growth nutrients.

  • Hair loss medications are also available and may help with temporary hair loss caused by phentermine.

When navigating hair loss while taking phentermine, it’s best to connect with a healthcare provider to discuss your options.

Hims offers online consultations, allowing you to seek hair loss advice from home at a time that fits your schedule. Get started today!

10 Sources

  1. Phentermine. Medline Plus. Retrieved from
  2. Almohanna, H., Ahmed, A., Tsatalis, J., et al., (2019). The Role of Vitamins and Minerals in Hair Loss: A Review. Dermatology and Therapy. Retrieved from
  3. Guo, E., Katta, R., (2017). Diet and hair loss: effects of nutrient deficiency and supplement use. Dermatology Practical and Conceptual. Retrieved from
  4. Asghar, F., Shamim, N., Farooque, U., et al., (2020, May). Telogen Effluvium: A Review of the Literature. Cureus, 12(5): e8320. Retrieved from
  5. Hoover, E., Alhajj, M., Flores, J., (2020, July 27). Physiology, Hair. StarPearls. Retrieved from
  6. Zinc. National Institutes of Health. Retrieved from
  7. Iron. National Institutes of Health. Retrieved from
  8. Biotin (2020). Medline Plus. Retrieved from
  9. Badri, T., Nessel, T.A. & Kumar, D.D. (2020, May 4). Minoxidil. StatPearls. Retrieved from
  10. U.S. Food and Drug Administration. (FDA). Adipex-p (phentermine hydrochloride) capsules label. Retrieved from
Editorial Standards

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Knox Beasley, MD

Dr. Knox Beasley is a board certified dermatologist specializing in hair loss. He completed his undergraduate studies at the United States Military Academy at West Point, NY, and subsequently attended medical school at Tulane University School of Medicine in New Orleans, LA. 

Dr. Beasley first began doing telemedicine during his dermatology residency in 2013 with the military, helping to diagnose dermatologic conditions in soldiers all over the world. 

Dr. Beasley is board certified by the American Board of Dermatology, and is a Fellow of the American Academy of Dermatology.

Originally from Nashville, TN, Dr. Beasley currently lives in North Carolina and enjoys spending time outdoors (with sunscreen of course) with his wife and two children in his spare time. 





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