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How Does Finasteride Impact Testosterone Levels

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 3 Oct 2023

Finasteride is a commonly prescribed medication used to treat pattern hair loss (androgenetic alopecia) and prostate enlargement in men. It works by inhibiting the enzyme 5-alpha-reductase, which converts testosterone into dihydrotestosterone (DHT).

Finasteride 1mg Tablets
Finasteride 1mg Tablets
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This leads many to wonder - does finasteride lower testosterone levels? This comprehensive guide will explore the science behind finasteride and testosterone. You'll get evidence-based answers on the short and long-term effects of finasteride on testosterone.

We'll also bust some common myths, discuss potential side effects, and look at natural alternatives. Whether you're contemplating using finasteride or are already on this journey, we at The Independent Pharmacy aim to help you understand how this medication impacts your testosterone levels.

Understanding Testosterone

Testosterone is the primary male sex hormone, though women also produce small amounts. It plays a crucial role in the development of male reproductive tissues and secondary sexual characteristics. Testosterone also helps maintain muscle mass, bone density, red blood cell production, and a healthy libido. The testes produce most testosterone, stimulated by luteinising hormone from the pituitary gland. Testosterone circulates throughout the body, loosely bound to proteins. A small fraction of testosterone is converted to DHT by 5-alpha-reductase inhibitors in tissues like the prostate and hair follicles. DHT binds more tightly to androgen receptors, amplifying testosterone's effects.

Maintaining normal testosterone levels is important for men's health. Having low testosterone can be a challenging experience, as it's linked to decreased energy, infertility, erectile dysfunction, emotional struggles, and muscle loss.

What's the Difference Between Testosterone and DHT?

Testosterone and dihydrotestosterone (DHT) are both androgen hormones that play important roles in men's health. However, there are some key differences:

  • Origin - Testosterone is produced primarily in the testes. DHT is converted from testosterone by the enzyme 5-alpha-reductase in tissues like the prostate.
  • Potency - DHT is a more potent androgen than testosterone, binding about 3 times more tightly to androgen receptors that regulate gene expression and masculine traits.
  • Levels - Testosterone is present at much higher levels, around 10 times higher than DHT in men.
  • Roles - Testosterone is crucial for sexual development, muscle growth, bone strength, and sex drive. DHT helps develop male reproductive tissues and influences hair growth patterns.
  • Side effects - Excess testosterone can lead to aggressive behaviour, acne, and testicular shrinkage. Excess DHT is associated with prostate enlargement and pattern baldness for those genetically prone.
  • Suppression - Lowering testosterone causes more significant effects on energy, sexual function, and muscle mass. Lowering DHT primarily impacts prostate health and hair loss.

While DHT is a more potent androgen, testosterone circulates at higher levels and is more critical for overall men's health and vitality. Both hormones play complementary roles in male development and function.

Testosterone Test
Testosterone Test
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Does Finasteride Lower Testosterone?

By blocking the 5-alpha-reductase enzyme, finasteride prevents the conversion of testosterone to DHT. This leads to increased testosterone levels, as less is being converted to DHT. In clinical studies, men taking finasteride had 9-15% higher testosterone levels compared to placebo after 3-12 months of treatment.

However, this rise in testosterone is offset by a couple of factors. First, the body adapts to higher testosterone by reducing luteinising hormone secretion from the pituitary.

This leads to lower testicular production of testosterone. Second, more testosterone binds to albumin and other proteins, reducing the amount of free testosterone available to tissues.

The net result is that total and free testosterone levels are ultimately unchanged with long-term finasteride use.

Short-term vs. Long-term Effects on Testosterone

In the first few months of continued treatment, finasteride tablets can cause a transient rise in testosterone levels by blocking its conversion to DHT.

In a study, finasteride increased total testosterone by 9.1% compared to baseline. However, this effect diminished over time. By one year, testosterone levels were similar to pretreatment and remained stable with continued use.

In a placebo-controlled trial, there was no significant difference in testosterone levels between the finasteride and placebo groups. Both maintained normal testosterone throughout the study. These findings confirm finasteride has minimal long-term impact on testosterone levels.

Adverse Side Effects Related to Testosterone Levels

While finasteride does not significantly alter testosterone levels, its effects on DHT and neurosteroids may contribute to sexual adverse effects in some men. These include:

Erectile dysfunction - Difficulty achieving or maintaining erections. Studies show no link to decreased testosterone.

Low libido - Reduced sex drive. It may be related to changes in brain neurosteroids.

Ejaculation disorders - Decreased volume, reduced force, pain. Likely due to lower DHT.

Gynecomastia - Breast tissue growth. This can occur if the testosterone/estrogen ratio gets thrown off.

Mood changes - Increased depression and anxiety. Unclear if it is related to testosterone.

We know that the possibility of sexual side effects can be concerning. However, it's worth noting that these occur in a small percentage of cases—around 3-5% in clinical trials—and are generally reversible upon stopping the medication.

Natural Alternatives to Finasteride

If you're looking for natural alternatives to finasteride, there are several options you can discuss with your healthcare provider. These include saw palmetto, pumpkin seed oil, and various lifestyle changes. We understand that each individual's journey is unique, so it's important to consult with a healthcare professional for personalised advice. However, have realistic expectations about their effectiveness and safety compared to finasteride. Thoroughly research any alternatives before using them.

  • Saw Palmetto - Herbal extract that may inhibit 5-alpha-reductase. Less effective than finasteride.
  • Pumpkin Seed Oil - Contains phytosterols that may block DHT. Minimal research on efficacy.
  • Laser Devices - Low-level laser light devices may stimulate hair growth. The evidence is weak.
  • Microneedling - Creates micro-injuries in the scalp to boost hair growth factors. Evidence is limited.
  • Diet & Exercise - Optimising nutrition intake and activity levels may help improve testosterone naturally.
  • Stress Reduction - Managing stress can increase testosterone. Activities like yoga and meditation help.
  • L-Lysine - This essential amino acid may help block DHT production. Requires further study.
  • Zinc Supplements - Zinc is needed for testosterone production. It may prevent hair loss in deficiency.

When considering natural alternatives, look for options with scientific backing and few side effects. Have realistic expectations, as natural approaches tend to be modestly effective compared to finasteride. Consult a doctor before discontinuing any medications.

Frequently Asked Questions

We understand how distressing experiencing side effects can be, and we are here to help you understand all of your options. Here are answers to some common questions about finasteride and testosterone from people like you:

Can finasteride cause low testosterone?

No, multiple studies confirm finasteride has little long-term effect on testosterone levels. Any transient increase is offset by the body's adaptation.

Do DHT blockers lower testosterone?

While they block the conversion of testosterone to DHT, clinically, they do not lower total testosterone concentrations. Both DHT and testosterone stay in the normal range.

Why does finasteride cause ED if it increases testosterone?

Despite a temporary rise in testosterone, finasteride does not improve erectile function. Sexual side effects are likely related to lower DHT levels, not testosterone changes.

Can finasteride cause permanent damage?

In most men, side effects are reversible upon stopping treatment. There is no evidence finasteride causes permanent infertility, sexual dysfunction, or hormone changes in the majority of men. However, some men may experience persistent symptoms post-treatment.


In summary, finasteride actually causes a transient rise in free testosterone levels, though over the long term there are minimal impacts on overall level.

Multiple clinical studies have shown finasteride does not significantly alter total or free testosterone concentrations. Changes in DHT and neurosteroids likely mediate sexual side effects, not reductions in testosterone.

Though side effects are reversible for most men, some may experience persistent symptoms after stopping long-term treatment. For those seeking natural alternatives, options include herbal supplements, diet and lifestyle changes.

However, these have less scientific evidence backing their efficacy. Talk to your doctor for appropriate medical advice and determine if finasteride is appropriate for your health needs.


Finasteride-Its Impact on Sexual Function and Prostate Cancer - PMC (

Effects of finasteride on serum testosterone and body mass index in men with benign prostatic hyperplasia - PubMed (

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