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How Does the Half-Life of Finasteride Affect Your Hair Loss?
Dr Barry Abdelrahimsai (GMC)
Medically reviewed by
Dr Barry Abdelrahimsai (GMC)
Updated on March 21, 2024

While it has excellent results in treating male pattern baldness, the half-life of Finasteride is only between 4.7 and 8 hours [1]. This means that it only remains in your system for a relatively short time after taking it. This may have implications for your hair loss, as well as for the side effects you may be experiencing.

The good news is that if you stop your Finasteride treatment, any adverse reactions should normally resolve within a few days. However, the bad news is that your hair shedding may return to its pre-treatment rates approximately 4 days after you stop taking this medication [1].

Keep reading this article to learn everything you need to know about:

  • How Finasteride works to curb male pattern baldness
  • The impact of Finasteride half-life on its effectiveness against hair shedding
  • The relationship between the half-life of Finasteride and its side-effects
  • Finasteride alternatives and their respective half-life
Table of Contents

How does Finasteride treat your hair loss?

It is a scientifically proven fact that Finasteride can really work in curbing androgenetic alopecia (male pattern baldness). Studies show that 83% of men who used this medication showed no further hair loss [2] and 87% even experienced Finasteride hair regrowth [3]. 

This medication works by decreasing the activity of an enzyme called 5 alpha-reductase, which converts your body’s naturally occurring testosterone into a different male hormone called dihydrotestosterone (DHT). Excessive DHT production is the main cause of androgenetic alopecia, as it binds to androgen receptors in your hair follicles, preventing them from producing hair. So basically, Finasteride plays a role in lowering the levels of DHT in your blood, which can cause hair loss and prevent regrowth. 

What is the Finasteride half-life?

All pharmaceutical substances have a half-life. This term refers to the amount of time it takes for half of the administered substance to leave your system, either by being metabolised (used by your body) or eliminated.

Since, in many cases, medication still has effects on your body even at lower concentrations (i.e. after the passing of a few half-life periods), knowing its half-life is useful in determining the therapeutic dose you need and how frequently you should take it. Drugs with a longer half-life can be prescribed at smaller daily doses, as they retain sufficient concentration in your blood over time to cover the window between administrations.

The half-life of Finasteride can differ with the age of the patient who is taking this treatment. Normally, it takes between 4.7 and 7.1 hours for half of the Finasteride 1 mg dose you have taken to be eliminated from your system [1]. However, in men over the age of 70, it can take up to 8 hours [4].

Finasteride molecular structure

How long does Finasteride stay in your system after you stop taking it?

Considering that the mean half-life of this medication is 4.8 hours, that means it normally takes just under 5 hours for a healthy adult male to eliminate half of the drug from his system [2]. Within another 5 hours, half of the remaining quantity will be eliminated, only leaving a quarter and so on. That means it shouldn’t take more than a couple of days for a 1 mg or even 5mg Finasteride dose to completely leave your system.

How does the half-life of Finasteride affect your hair loss?

Like most hair loss treatments, Finasteride is only effective for as long as you are taking it. Since a single dose of this medication can, on average, suppress the levels of DHT in your blood for up to 4 days [1], once that effect is gone, the quantity of this male hormone will start to increase once more. That means your hair shedding will resume as well. 

The almost 5-hour half-life means that missing a Finasteride dose every now and then is unlikely to have serious repercussions on your hair. That is because enough active substance to reach the minimum effective concentration is still left in your bloodstream

The minimum effective concentration of a treatment represents the lowest concentration of a drug which is sufficient to produce the desired clinical effect. The minimum toxic concentration is the threshold after which you start to develop unwanted side effects.

The optimal range of Finasteride blood concentration falls between these two minimums and taking it as prescribed is the best way to secure this. So, taking your treatment consistently and making sure you don’t often miss or double doses can help you achieve the best results for your hair thinning.  

How Does the Half-Life of Finasteride Affect Your Hair Loss

How does Finasteride’s half-life relate to its side effects?

While more evidence is needed to establish a clear connection between Finasteride and its reported side effects, a small proportion of its users have experienced adverse reactions while taking this medication. The most commonly reported ones include [5][6][7]:

Multiple studies have determined that normally, these symptoms resolve in a few days or weeks after the medication leaves your system [6]. However, a small number of patients reported experiencing persistent side effects months and even years after treatment cessation. This still understudied and unproven condition was dubbed Post-Finasteride syndrome

Normally, since the half-life of Finasteride is only a few hours long and its hair loss effect only lasts as long as a few days, you would expect its side effects to also fade after a similar amount of time (which does indeed happen in most cases). Possible explanations for Post-Finasteride syndrome include [6][8]:

  • Long-lasting changes brought by Finasteride to the neurotransmitter and hormone makeup of certain users.
  • Somatizations caused by the nocebo effect (being overly mindful of a medication’s side effects can trick your body into experiencing them)
  • Mere coincidence – the persistent symptoms may not be caused by Finasteride use, but simply develop alongside your treatment.
man using topical hair loss treatment

The half-life of the most effective Finasteride alternatives

If you are considering Finasteride alternatives for your hair thinning, you may be interested in their half-life as well. The most effective substitutes for this medication are Dutasteride and Minoxidil

Dutasteride reduces hair thinning through the same mechanisms as Finasteride. However, it has a significantly longer half-life: approximately 5 weeks, which means it can take as long as half a year or more to clear it out of your system [9] (but also that a lower daily dose – 0.5 mg –  will be sufficient to treat your hair loss). This medication has also been found to be more effective in treating male pattern baldness than Finasteride [10]. However, it has not yet been approved for hair loss and can only be prescribed off-label.

Topical Minoxidil works by dilating the blood vessels in your scalp to allow more oxygen and nutrients to reach your hair follicles. It is also very effective in curbing androgenetic alopecia and has fewer reported side effects. Moreover, using Minoxidil combined with Finasteride enhances both their effectiveness. While oral Minoxidil has a rather short half-life, of merely 3 hours [11], topical Minoxidil has a significantly longer one – approximately an entire day [12].

Are you looking for a permanent solution to your hair loss?

Regardless of the type of hair loss medication you opt for, their effect will normally fade shortly after they have left your system. This means that if you want to maintain any improvement in your hair shedding, you have to keep taking them forever. However, there is one extremely successful treatment for male pattern baldness that can treat your hair thinning once and for all.

While many are aware that hair restoration surgery is growing ever more popular and affordable, much fewer know that a hair transplant is permanent. That means in most cases, you undergo this painless, outpatient procedure once and can enjoy fuller, thicker hair for decades to come. Here is what a hair transplant can look like after 10 years.

If you are interested in learning more about how you can get a natural-looking hair transplant, simply book a free hair transplant consultation with one of our top-tier surgeons. They will patiently walk you through the entire procedure, answer all of your questions and perform a thorough examination to determine if you make a good candidate for hair restoration surgery.

How Does the Half-Life of Finasteride Affect Your Hair Loss?, Wimpole Clinic

Dr Barry Abdelrahimsai (GMC)
Medically reviewed by Dr Barry Abdelrahimsai (GMC)Updated on March 21, 2024
The Wimpole Clinic offers FUE Hair, Beard & Eyebrow Transplants & Trichology.
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