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Can Phentermine Cause Hair Loss?

Kristin Hall, FNP

Reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Published 12/04/2022

Updated 12/05/2022

Can phentermine cause hair loss? If this question has been keeping you up at night, you’re not alone.

Imagine this: You start taking an appetite suppressant with the hopes it’ll reverse some recent weight gain,a and — bam! — you suddenly notice a loss of head and body hair. 

Some say this exact thing can happen with the weight loss medication phentermine. For obvious reasons, you’d want to know if any type of hair loss is associated with this medication when taking it.

Lucky for you, we’re answering the question: Can phentermine cause hair loss? Read on for all the details.

What Is Phentermine? 

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

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

While phentermine may not lead to rapid weight loss, it has been shown to be effective at helping people 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 administered for three to six weeks. 

Common Side Effects of Phentermine

There are some common adverse effects associated with taking this medication for weight loss. Some of the more benign phentermine side effects include: 

  • Vomiting

  • Constipation

  • Diarrhea

  • Dry mouth

  • Unpleasant taste in your mouth

There are some more serious 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, contact your healthcare provider as soon as possible.

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

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Can Phentermine Cause Hair Loss? 

At this point, you know phentermine can cause things like nausea and vomiting or, more seriously, blood pressure changes. But can taking phentermine cause hair thinning or loss? 

The answer isn’t exactly black and white. There’s no evidence that phentermine alone causes hair loss.

However, if you’re taking phentermine and lose your appetite, you may not get as many nutrients in your diet as you need. 

Being deficient in the following vitamins and micronutrients may cause non-scarring alopecia (a type of hair loss):

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

  • Vitamin D

  • Vitamin E

  • Iron

  • Zinc

Why does this happen? Vitamins and minerals play a vital role in the normal hair follicle cycle and cell turnover. When these things go haywire, hair loss can occur.

Why Does Phentermine Cause Hair Loss? 

To get more specific, if you take phentermine and lose your appetite to the point where you’re not getting enough hair health-boosting nutrients, something called acute telogen effluvium can occur

Telogen effluvium essentially means you are experiencing excessive shedding of your hair.

To understand the reason behind this fallout, you need 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, hair releases from its follicles. As a result, you may see an increase in hair shedding and loss. Things like nutritional deficiencies can shorten this phase.

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How to Reverse Hair Loss from Phentermine

If you’re taking phentermine and notice excessive hair loss, the first thing you should do is reach out to your healthcare provider. 

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

Here are some things that may be discussed as options for treating your hair loss. 

Make Adjustments to Your Diet

As mentioned, it’s likely not the phentermine specifically that’s causing your hair loss. Rather, it could be the fact that this medication lowers your appetite, so you may not be getting the kind of nutrients you need to keep your hair healthy. 

Zinc and iron are two major nutrients you need for healthy hair growth. Eating crab, cashews and oatmeal can help you get more zinc. For iron, you could try and eat more spinach and seafood.

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

Or, if you can’t get enough biotin through a balanced diet, you could take the biotin gummy from Hims. It also contains vitamin D, which, as we mentioned above, is needed for hair health. 

Try a Hair Loss Medication

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

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

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 can be a good option to use alongside one of the above suggestions. 

One you could try: The thickening shampoo from Hims. It contains saw palmetto, a natural ingredient thought to help with hair loss.

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Hope and Help for Hair Loss

Whatever you decide to try, know this: Telogen effluvium tends to be reversible. 

If you notice hair loss after you start taking phentermine, it may be because you’re getting enough of certain nutrients. Phentermine is a weight loss medication that suppresses your appetite. If you’re not hungry, you may not eat enough to get those nutrients, which could cause hair loss. 

When navigating hair loss while taking phentermine, it’s best to connect with a healthcare provider to discuss options. Hims offers online consultations, allowing you to seek hair loss advice at a time that easily fits your schedule. Get started today!

9 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
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.

Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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