Does phentermine cause hair loss?

In this article:

• Can phentermine cause hair loss?
• Is hair loss from phentermine reversible?
• How to stop hair loss from phentermine
• The bottom line

In this article

• Can phentermine cause hair loss?
• Is hair loss from phentermine reversible?
• How to stop hair loss from phentermine
• The bottom line

Phentermine is a commonly prescribed weight loss drug. When paired with diet and exercise, this appetite suppressant can accelerate weight loss, and millions of Americans have used it successfully. But will it thin your hair along with your body? It’s not inherently linked to hair loss (alopecia), but some people have reported losing hair while taking phentermine. Here are the important details. 

Can phentermine cause hair loss?

The label for Adipex-P—a brand name of phentermine—doesn’t list hair loss as a common side effect. That’s because the medication itself doesn’t cause it. Instead, it reduces feelings of hunger by stimulating norepinephrine release in the hypothalamus. This process activates the body’s “fight or flight” response, which can suppress the appetite but doesn’t directly influence hormones or other hair growth mechanisms.

Phentermine’s mechanism of action might not lead to alopecia, but it could indirectly influence hair loss. According to Dr. Shahinaz Soliman, MD, founder of Shantique Medspa, “This is mainly given the way the drug affects the metabolic system of the body, leading to stress in the hair follicle.” These effects include:

• Nutrient deficiency: A reduced appetite means you feel less hunger and eat fewer calories. “Hair loss may result from reduced nutrient intake due to eating less,” says Dr. Viktoryia Kazlouskaya, MD, Ph.D., board-certified dermatologist and owner of Dermatology Circle PLLC. “Monitoring and ensuring adequate nutrient levels can help address this issue.” Vitamins and minerals are vital to new hair growth, especially vitamins A, B, D, E, iron, selenium, and zinc.

• Rapid weight loss: Hair loss from an especially fast drop in weight is a type of telogen effluvium, or alopecia, that occurs after a significant body change. Fortunately, it’s typically temporary—a case of accelerated natural shedding—and the hair should grow back after the body stabilizes.
• Hormone changes: A study on postmenopausal women concluded that weight loss can alter the levels of sex hormones, which can play a role in hair growth and hair thinning.

Hair loss is a somewhat common issue among weight loss drugs. In fact, in 2023, the FDA began investigating alopecia associated with the popular GLP-1 drugs (Ozempic, Wegovy, etc.). Unlike phentermine, however, some of those medications showed hair loss as a potential side effect during clinical trials. In the trials for Zepbound (tirzepatide), for example, up to 5.7% of participants reported alopecia, compared to 1% who took a placebo (inactive medicine).

Is hair loss from phentermine reversible?

“This type of hair loss is usually not permanent, but it may be controlled by correct dieting, vitamin supply, and stress reduction,” Dr. Soliman says. This kind of alopecia that stems from medications or weight loss is called telogen effluvium.

According to the Journal of Clinical & Diagnostic Research, telogen effluvium shedding usually takes 3–6 months to stop, and hair regrowth will start 3–6 months after the initial cause is removed. However, cosmetically significant regrowth can take 12–18 months.

So, if that’s the cause of your hair loss, it might just be a waiting game after you stop treatment and stabilize your weight. Things get a little more complicated if telogen effluvium isn’t the cause. Male pattern hair loss, female pattern hair loss, and hair loss from thyroid issues aren’t always as reversible. These don’t come from weight loss drugs or rapid weight loss, but they’re easy to confuse with telogen effluvium. If your thinning continues after you stop taking phentermine and losing weight, consult a healthcare provider about other possible treatment options.

How to stop hair loss from phentermine

Regrowing hair and slowing down hair loss are two different things, but they have some of the same solutions. “Drug-related hair loss is usually reversible, but the outcome can vary for each individual,” Dr. Kozlovskaya says. “No definitive prognosis can be made without understanding the personal situation and obtaining an exact diagnosis.”

That said, here are a few hair loss treatments that might stop it from getting worse.

• Eat a well-balanced diet: As we’ve already mentioned, getting adequate vitamins and minerals is essential to hair health. Make sure to include fruits, vegetables, and quality protein. See a doctor or nutritionist for help or to find out if supplements like biotin, zinc, or other nutrients might be a good option.
• Adjust your dose: Sometimes, a lower dose of phentermine—or a short break from the medication—can help. Of course, talk to your doctor before making any sudden changes to your treatment regimen.
• See a dermatologist: A healthy scalp can go a long way in fighting hair loss or regrowing hair follicles. “If hair shedding is severe, a dermatologist should be consulted to screen for other causes of hair loss and, at times, a different medication may be advised,” Dr. Soliman says. Since hair is part of the scalp, a dermatologist can diagnose the root cause and determine the best treatment.

• Try hair loss medications: Over-the-counter products like Rogaine (minoxidil) and prescription medications like Propecia (finasteride) can slow hair loss and promote regrowth. Consult a doctor to find out which hair loss drugs might work best for your condition.
• Manage stress: We know. It’s easier said than done, but studies have suggested that chronic stress can lead to graying and hair loss. Sometimes, stress is inevitable, but things like meditation, exercise, and mental health therapy can help.
• Protect your hair: Healthy hair is less likely to fall out. According to Dr. Kozlovskaya, “gentle hair care may help slow down hair loss.” So whenever possible, avoid tightly pulled hairstyles, harsh treatments or products, and excessive sun exposure. These can all damage your hair, increasing your chances of losing it.
• Try ketoconazole shampoo: This is primarily used as an antifungal treatment, but a study on female pattern hair loss demonstrated an ability to promote hair regrowth as well.

Which of these will work best depends on your circumstances and medical conditions. Consult a healthcare professional for medical advice on which might be most effective.

The bottom line

Phentermine can be a powerful weight loss medication for certain individuals diagnosed with obesity, especially when it complements exercise and a well-rounded diet. And while it doesn’t directly cause hair loss, some people have still reported experiencing it. However, temporary hair loss issues like telogen effluvium can come from nutrient deficiencies or other bodily changes associated with rapid weight loss.

Fortunately, there are ways to prevent or reverse these conditions. So, if you notice hair loss while taking phentermine, talk to a dermatologist or other doctor about how you can best manage it.