Why Does Finasteride Cause Shedding?

It is an awkward thing that a hair loss treatment can actually cause hair to fall out rather than the reverse. Finasteride is a well- known drug that is used for pattern hair loss or baldness, however, it is commonly associated with shedding. A condition of losing hair in an amount greater than normal. But, how can the cure lead to more damage? In the following article, we will have a glance on that and get to understand how finasteride might cause shedding and at the same time maintains its effect of improving hair count.
Thinning hair pulled back
Universally, androgenic alopecia (AGA) is the most common form of pattern hair loss. Studies revealed that the prevalence of AGA in men reaches 87%. About 5% of males demonstrate AGA by the age of 20 years and almost 50% of men show that by 40 years. Data considering female AGA is less clear but is suggesting that approximately 30% of them demonstrate and evidence of AGA at the age of 30 years.

Finasteride is a medication that was originally developed for treating benign prostate hypertrophy in 1992. It inhibits an enzyme called 5-α-reductase, which is responsible for the conversion of testosterone to dihydrotestosterone. The presence of 5-α-reductase in both prostate and inner line sheath of the hair led to the investigation of finasteride for the treatment of (AGA) or pattern hair loss in men.

In general, finasteride is stated to be a safe and tolerable medication with high effectiveness. The clinical efficacy of that drug was reported in many pieces of literature. A reported study that included men of (18-41) years old, increased hair count in 80% of the finasteride-treated group was marked to the placebo patients (receiving no drug) in the first year of treatment. At three years, 77% of the former group showed improvement compared to the latter group. In another study that involved 1,215 patients, the therapeutic effect of finasteride was observed after the third month. At the beginning of the treatment, there was on average 876 hairs per area of 2.54 cm/diameter circle. After a year of treatment, there was a mean increase of 107 hairs per area, and after two years, 138 hairs per area. In the placebo group, there was no improvement at that time, and androgenetic alopecia continued progressing. Besides the improvement in hair counts, there was also a decrease in the hair loss and an improvement of hair volume. Of the reports revealing that finasteride not only increases the amount of hair but also improves its appearance is one in which the patients recorded a doubled anagen/telogen ratio, compared to the one they started the treatment with. What are anagen and telogen? It seems like this ratio increment is an indication of the finasteride success in the therapy. Well, you are right and that will come in a bit.

But, let’s get first of what you might be wondering about- side effects, can they include shedding? Is it possible? Well, we remember that finasteride works by blocking dihydrotestosterone which is a male sex hormone and is also a form of testosterone. In clinical tests, approximately 2% of the people who take finasteride reported unwanted sexual side effects. Of that 2%, half of them reported that the side effect went away after taking the medication for three months, and everyone reported that the side effects went away as soon as they discontinued the medication. So, that leaves less than 1% of guys taking finasteride would have the chance of developing sexual side effects.

Shedding was not included within the last paragraph because it is not a side effect of finasteride but a normal thing that need not worry about. To have the full picture of that, we will get into the hair cycle.

The hair growth cycle is continuous and on a regular day, 90% of the hair is in the latent phase while the other 10% is either growing or shedding. The different stages through which the hair goes through are summarized next:

  • It starts with the anagen or growing phase. During this stage, the hair shaft is being increased through the division of cells in the root of the hair. The duration of this goes back to the genes; it can take from 2 to 7 years and determines the length of the hair. Although the hair is technically dead, a healthy hair care regimen can keep it looking beautiful while it’s in the anagen phase.
  • Next is the catagen stage (Transition phase) and is consisting of a 2-3 week transitional period in which the hair is no longer growing. During this stage, a club hair is formed that occurs when the section of the hair follicle attaches to the hair shaft, cutting the follicle off from its blood supply and the cells that produce new hair. This club hair leads to the next stage.
  • The third phase is the telogen or resting phase. This last for 1 to 3 months. In it, the lost hair during the past phases begins to grow again to produce new hair.
  • The final stage is usually considered a part of the previous one, yet some take it as a separate phase. It is the exogen or the shedding phase. Here, the old hair sheds at a normal rate of 50 to 150 hairs can fall out daily.

pharmacist posing with medication
Factors like chronic stress, extreme malnutrition, certain medications and chronic serious illnesses can cause excessive shedding that is termed Telogen Effluvium. The most characteristic thing about this is that it is temporary; it occurs in response to the triggering factor and luckily goes off when it does the same. If exposure to the trigger is brief and there are no other contributing factors, then the shedding may last for around 3 months and then recover so that 6 months later the hair is pretty much back to normal.

So, for a person that is not using finasteride or any hair loss treatment, excessive hair loss is something to look at. Yet, if you are using finasteride, don’t panic or decide that you are not responding to treatment. Don’t also settle for the claim that the drug is not working for you or go further and say that God has forsaken you. What you are being through is so normal, it is possible, and as mentioned above, rather common. The amount of hair shed varies from person to person and it is only a matter of time before you have a stronger and healthier hair.



  • Drake LA, Dinehart SM, Farmer ER, Goltz RW, Graham GF, Hordinsky MK, Lewis CW, Pariser DM, Webster SB, Whitaker DC. Guidelines of care for androgenetic alopecia. American Academy of Dermatology. Journal of the American Academy of Dermatology 1996;35:465.
  • Olsen EA. Female pattern hair loss. Journal of the American Academy of Dermatology 2001;45:S70-S80.
  • Gormley GJ, Stoner E, Bruskewitz RC, Imperato-McGinley J, Walsh PC, McConnell JD, Andriole GL, Geller J, Bracken BR, Tenover JS. The effect of finasteride in men with benign prostatic hyperplasia. New England Journal of Medicine 1992;327:1185-91.
  • Kaufman KD, Olsen EA, Whiting D, Savin R, DeVillez R, Bergfeld W, Price VH, Van Neste D, Roberts JL, Hordinsky M. Finasteride in the treatment of men with androgenetic alopecia. Journal of the American Academy of Dermatology 1998;39:578-89.
  • Libecco JF, Bergfeld WF. Finasteride in the treatment of alopecia. Expert Opinion on Pharmacotherapy 2004;5:933-40.
  • Van Neste D, Fuh V, Sanchez‐Pedreno P, Lopez‐Bran E, Wolff H, Whiting D, Roberts J, Kopera D, Stene JJ, Calvieri S. Finasteride increases anagen hair in men with androgenetic alopecia. British Journal of Dermatology 2000;143:804-10.
  • Stoner E. The clinical development of a 5α-reductase inhibitor, finasteride. The Journal of steroid biochemistry and molecular biology 1990;37:375-78.
  • Mysore V. Finasteride and sexual side effects. Indian dermatology online journal 2012;3:62.
  • Courtois M, Loussouarn G, Hourseau C, Grollier JF. Hair cycle and alopecia. Skin Pharmacology and Physiology 1994;7:84-89.
  • Alonso L, Fuchs E. The hair cycle. Journal of cell science 2006;119:391-93.
  • Hadshiew IM, Foitzik K, Arck PC, Paus R. Burden of hair loss: stress and the underestimated psychosocial impact of telogen effluvium and androgenetic alopecia. Journal of investigative dermatology 2004;123:455-57.
  • Harrison S, Sinclair R. Telogen effluvium. Clinical and Experimental Dermatology: Clinical dermatology 2002;27:389-95.