Androgenetic alopecia, also known as pattern hair loss, is an inherited condition that causes a receding hairline and hair thinning on the top and front of the head. It is one of the most common causes of hair loss and the most common cause of balding.
Finasteride, commonly known by the brand name Propecia®, is FDA-approved for the treatment of androgenetic alopecia in men. It’s sold as a prescription-only medication in the form of 1-milligram tablets meant to be taken once a day. (1-5)
Men experience slowed hair loss and increased hair regrowth within the first 4 months to 1 year of continuously taking finasteride.(1,10) But early on in treatment, finasteride shedding can affect your hair. This temporary side effect, which occurs during the first weeks to months of use, is normal and usually stops within the first 6 months.
Using Finasteride for Hair Loss
Finasteride is a medication that can help stop androgenetic alopecia. As the name suggests, androgens, a type of hormone, are partially responsible for this form of hair loss. People with androgenic alopecia inherit an increased sensitivity to dihydrotestosterone (DHT), an androgen that binds to hair follicles and shortens the growth phase of the hair growth cycle. (3)
DHT causes the scalp’s hair follicles to shrink. This results in your normal, long, pigmented hair strands (terminal hairs) being replaced by shorter, thinner, non-pigmented hair strands (vellus hairs). (6)
Over time, the usual 3 to 6-year duration of hair growth decreases to months or weeks. Eventually, DHT can stop hair growth altogether, resulting in balding. Finasteride works by stopping the DHT hormone’s negative effects on hair growth. (6)
How Does Finasteride Work?
Finasteride is a DHT blocker. When DHT binds to hair follicles, it causes a gradual shrinkage known as miniaturization. Thinner, weaker hair strands start to grow from these follicles. Over time, hair growth can stop completely.
Blocking DHT prevents the progression of hair thinning and hair loss, allowing hair to regrow. A daily dose of finasteride blocks DHT levels in scalp hair follicles by 70% or more within weeks. Blocking DHT slows hair loss and promotes thicker, healthier hair regrowth within 12 months.(1-5)
You should know: It’s important to continue treatment to sustain these improvements in hair regrowth. Discontinuation of finasteride results in DHT levels returning to normal within 14 days. You’ll be likely to see a reversal of hair regrowth improvements within a year. (7-10)
Is There a Shedding Phase With Finasteride?
Within 1 to 3 months after beginning finasteride treatment, people can expect to see temporary hair shedding. This type of hair loss, called finasteride shedding, is normal and lasts around two weeks.
Although it can be unnerving, it is one sign that the treatment is working. After experiencing finasteride shedding, slowed hair loss and hair regrowth will occur in 3 to 4 months. More significant hair regrowth occurs within 12 months. (10-12)
Other hair loss treatments can also cause hair shedding. Examples include minoxidil (in which case, this side effect is called ‘minoxidil shedding’) and dutasteride (‘dutasteride shedding’). (13,14) Finasteride shedding is not permanent and it’s unrelated to hair loss disorders.
What Does Finasteride Shedding Look Like?
Everyone experiences daily hair shedding of around 100 hairs a day as part of the hair growth cycle. This is part of a three-stage hair growth cycle that all healthy hair follicles experience.
The active hair growth (anagen) phase lasts 2 to 8 years. New hair only grows during the anagen phase. The second phase is a brief transitional (catagen) phase of 2 to 3 weeks, followed by a resting (telogen) phase lasting up to 3 months. At the end of the telogen phase, the hair is shed, and a new hair strand replaces it. Then, the hair growth cycle starts over. (11)
DHT shortens the anagen phase, interfering with hair growth. As finasteride starts working to block DHT and DHT levels drop, thousands of hair follicles in the telogen phase simultaneously transition to the anagen phase. This induces synchronized, rapid new hair growth, pushing out the old resting hair and causing finasteride shedding.
Finasteride shedding generally occurs in the first few weeks of finasteride treatment. If you gently run your fingers through about 60 hair strands and less than a dozen hair strands fall, it’s likely normal hair shedding. If you shed more hair strands, then it’s likely finasteride shedding. (11,16)
The shedding timeline tends to be as follows (11):
- Finasteride shedding in the first month: Shedding is unlikely this early on.
- Finasteride shedding at 2 to 3 months: This is the most common phase when you may notice shedding. You may also start to notice new hair growth over the bald patch.
- Finasteride shedding at 6 months: Shedding due to the medicine usually stops within 6 months. At this stage, you should notice less hair loss and start to see new, healthy hair growth over balding areas.
- Finasteride shedding after a year: Any hair loss you see is unrelated to your treatment. Continued shedding requires evaluation by your healthcare provider.
How Long Does Finasteride Shedding Last?
Finasteride shedding is temporary and usually lasts a few weeks. In some rare cases, it can last for a month or two. It is important to contact your healthcare professional for advice if the shredding continues for more than a few months.
Hair shedding that lasts for more than a few months may be a sign of another health issue or cause of hair loss, like a nutrient deficiency. It’s sometimes indicative of a condition called telogen effluvium.
Telogen effluvium is commonly known as stress-related hair loss. It causes temporary hair thinning over the scalp, occurring after physical or emotional stress such as an illness or a major life event.
Telogen effluvium prematurely pushes many hair follicles into the resting state of the hair growth cycle simultaneously. This results in diffuse scalp hair loss within 2 to 4 months. Hair loss tends to fall out when shampooing or brushing hair, rather than in patches or clumps. (15)
Is Shedding on Finasteride a Good Thing?
Given that this side effect is temporary, you shouldn’t see finasteride shedding as a bad thing. It’s inconvenient, and you might need to vacuum around the house more than average – but focus on the positive: The shedding will eventually stop.
Finasteride shedding is a side effect that follows the hair growth cycle. This means it usually goes away within 2 months. Most users see healthier hair regrowth after 3 to 4 months of regular use.
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- Rossi, A., Cantisani, C., Melis, L., Iorio, A., Scali, E., & Calvieri, S. (2012). Minoxidil use in dermatology, side effects and recent patents. Recent Patents on Inflammation & Allergy Drug Discovery, 6(2), 130-136.
- Ghonemy, S., Alarawi, A., & Bessar, H. (2021). Efficacy and safety of a new 10% topical minoxidil versus 5% topical minoxidil and placebo in the treatment of male androgenetic alopecia: A trichoscopic evaluation. Journal of Dermatological Treatment, 32(2), 236-241.
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Last updated November 2023