Can I Take Finasteride and Testosterone Together?

Taking finasteride and testosterone together is not only possible but is a well-studied combination that physicians sometimes prescribe deliberately. The idea behind pairing them is straightforward: testosterone replacement treats low testosterone, while finasteride blocks one specific downstream product of testosterone that can cause unwanted effects on the prostate, scalp, and skin. Research spanning several decades has examined how the two drugs interact, and the findings paint a more nuanced picture than you might expect.

How the Two Drugs Interact in Your Body

Testosterone is converted into a more potent androgen called dihydrotestosterone (DHT) by an enzyme in your tissues. Finasteride specifically blocks the type 2 version of that enzyme, cutting off that conversion pathway.¹ When you take testosterone replacement therapy (TRT), your body naturally produces more DHT as a byproduct. Adding finasteride to the mix intercepts that process, so you get the benefits of having adequate testosterone while limiting DHT’s effects on tissues where it tends to cause trouble.

What makes this combination interesting is that testosterone and DHT do not affect every tissue the same way. Your muscles, bones, and fat cells respond mostly to testosterone itself, while your prostate, hair follicles, and sebaceous glands are far more sensitive to DHT. That division of labor is why the combination works as well as it does: you can selectively dial down DHT without losing many of testosterone’s benefits elsewhere in the body.

Muscles, Strength, and Body Composition

One of the first things people on TRT care about is whether finasteride will undercut their gains. A 36-month randomized trial in older men with low testosterone found that it does not. Men receiving testosterone alone gained about 3.8 kg of lean body mass, while men receiving testosterone plus finasteride gained about 3.6 kg — a difference so small it was not statistically meaningful. Both groups also lost fat mass, lowered LDL cholesterol, and improved grip strength compared to placebo.² Physical performance on timed functional tests improved by a similar margin in both groups, suggesting that DHT is not the hormone doing the heavy lifting when it comes to muscle function.

A separate randomized trial that used higher-than-replacement testosterone doses alongside finasteride confirmed the same pattern: muscle strength and lean mass increased significantly, body fat decreased, and finasteride did not blunt any of those effects.³ Even in a more extreme clinical scenario — a pilot study of men with chronic incomplete spinal cord injury receiving high-dose testosterone with finasteride — the combination increased whole-body lean mass by roughly 3 to 4 percent and knee extensor muscle size by 8 to 11 percent over 12 months.⁴

The takeaway for anyone worried about their gym results: the evidence consistently shows that blocking DHT does not reduce muscle or strength benefits from testosterone. Testosterone itself, acting through androgen receptors in muscle, appears to be the main driver.

What Happens to Your Bones

Bone density is another area where the combination performs just as well as testosterone alone. The same 36-month trial of older men found that testosterone therapy increased lumbar spine bone mineral density by about 10 percent in the testosterone-only group and about 9 percent in the testosterone-plus-finasteride group — both dramatically better than the roughly 1 percent change in the placebo group. At the hip, both treatment groups saw about a 2 percent increase versus a slight decline in the placebo arm.⁵

An earlier study looking at finasteride on its own (without added testosterone) also found that it did not reduce bone density, even though it lowered DHT. The researchers concluded that testosterone is likely the active hormone for bone metabolism, though estradiol — which testosterone is converted into through a different pathway that finasteride doesn’t touch — may also play a role.⁶ Either way, if you’re on TRT for bone health, adding finasteride is unlikely to compromise those benefits.

The Prostate Question

This is arguably the strongest clinical rationale for combining the two drugs. Testosterone therapy tends to stimulate prostate growth and raise PSA (the blood marker doctors track for prostate health). That’s a concern for older men who may already have benign prostate enlargement. Adding finasteride counteracts this effect quite directly. In the 36-month trial, PSA rose significantly in the testosterone-only group, while the testosterone-plus-finasteride group saw significantly less prostate growth than either the testosterone-only or the placebo group.⁵

The spinal cord injury study showed a similar pattern: prostate volume changes were smaller in the testosterone-plus-finasteride group than in the placebo group at both 6 and 12 months.⁴ Because DHT is the primary androgen driving prostate tissue growth, blocking its production effectively shields the prostate from much of testosterone therapy’s stimulatory effect. For men who need TRT but are at risk for prostate complications, finasteride provides a meaningful protective buffer.

Hair Loss and the Combination

For many people asking this question, hair loss is the real concern. If you’re taking testosterone — whether for hypogonadism, as part of gender-affirming therapy, or for other reasons — the resulting rise in DHT can accelerate male-pattern baldness in genetically susceptible individuals. Finasteride blocks the conversion that fuels this process.⁷

The logic is simple: testosterone alone doesn’t cause hair follicle miniaturization nearly as aggressively as DHT does. By taking finasteride alongside TRT, you reduce the DHT surge that would otherwise thin out your hair. This approach makes finasteride one of the first-line options for androgenetic alopecia in anyone receiving testosterone therapy.⁸

How much hair you actually keep depends partly on genetics. One study found that a specific repeat sequence in the androgen receptor gene (the GGC repeat) was associated with how well patients responded to finasteride — those with shorter repeats tended to see more improvement in hair loss.⁹ There’s no commercial genetic test widely available to predict your response, but it helps explain why some people get great results and others see only modest improvement.

Red Blood Cells and Hematocrit

Testosterone stimulates the production of red blood cells. That’s often a benefit — it can help with anemia — but it also carries a risk. Too many red blood cells thicken the blood, raising the risk of clots. One important question is whether finasteride would reduce this effect, since it might seem like blocking a testosterone metabolite could dampen erythropoiesis. It doesn’t. A study tracking red blood cell counts, hematocrit, and hemoglobin over 12 months found that testosterone raised all three significantly, and adding finasteride made no difference.¹⁰

This means that if you’re on the combination, you still need the same blood monitoring as someone on testosterone alone. Your doctor will want to check your hematocrit periodically. If it climbs too high, the usual interventions — adjusting dose, donating blood, or switching to a different dosing frequency — apply regardless of whether you’re also taking finasteride.

Sexual Side Effects and the Finasteride Debate

Finasteride has a well-known reputation for sexual side effects, and this is the area that generates the most anxiety when people consider adding it to testosterone. A subset of men taking finasteride report reduced libido and erectile difficulties.¹¹ In most cases, these side effects resolve after stopping the drug. But reports of a persistent condition — sometimes called post-finasteride syndrome — describe sexual, neuropsychiatric, and physical symptoms that continue for months or longer after discontinuation.¹²

The question is whether testosterone replacement changes this risk profile. Some clinicians have noted that because TRT raises your total testosterone levels — and finasteride further increases circulating testosterone by blocking its conversion to DHT — the combination might actually support sexual function better than finasteride alone. However, this is more clinical reasoning than hard evidence from large trials. The 36-month trials in older men did not report a signal of worsened sexual side effects in the combination group compared to testosterone alone, but they also were not specifically designed to detect subtle sexual dysfunction.

If you’re already on testosterone and worried about adding finasteride, it helps to know that DHT is not the only androgen involved in sexual function. Testosterone itself plays a major role, and the combination keeps testosterone levels at or above normal. That said, individual responses vary, and the small group of people who are highly sensitive to DHT changes may still notice effects.

Mood and Neurosteroids

A more subtle and less well-understood concern involves the brain. DHT is a precursor to certain neurosteroids — compounds that influence mood, anxiety, and cognitive function. Studies of men who used finasteride for hair loss and then stopped found altered levels of these neurosteroids in both blood and cerebrospinal fluid, along with depressive symptoms, even after discontinuation.¹³ Specifically, levels of progesterone metabolites that have calming effects on the brain were lower, while precursor steroids were higher, suggesting a bottleneck in the conversion pathway.¹⁴

These studies were small and looked at patients who had already developed persistent symptoms — they don’t tell us how common this neurosteroid disruption is across all finasteride users. Still, the findings are worth knowing about. If you notice new anxiety or mood changes after starting finasteride, particularly if they don’t fit your typical pattern, bring them up with your prescriber. Most discussions of finasteride side effects focus on sexual function and miss the neuropsychiatric dimension entirely.

Beard Growth and Other DHT-Dependent Traits

People sometimes worry that finasteride will prevent or reverse facial hair growth while on TRT. A large retrospective study of over 450 men taking finasteride or a related drug for hair loss found that beard thickness was generally maintained. The authors noted that because finasteride does not lower testosterone levels — only DHT — testosterone itself can still interact with androgen receptors in beard follicles and promote growth even when DHT is low.¹⁵ While some individuals may notice slightly slower beard development, the fear that finasteride will undo facial hair gains on testosterone appears overblown for most people.

Skin is another area where DHT plays a role. DHT stimulates sebaceous glands, which produce oil. Some people on TRT develop acne as their DHT rises. Finasteride has been studied as an acne treatment, though in that role it was less effective than other anti-androgens like spironolactone.¹⁶ If you’re dealing with oily skin or acne breakouts from TRT, finasteride may help to a degree, but don’t expect it to be a complete solution.

The Combination in Transgender Men

Transgender men on masculinizing testosterone therapy face a specific version of this dilemma. They want the deepened voice, body composition changes, and facial hair that testosterone provides, but some experience unwanted androgenetic alopecia as a side effect. A case series evaluating finasteride in transgender men undergoing TRT found it appeared safe and effective for treating hair loss without significantly undermining the masculinizing effects of testosterone.¹⁷ However, the researchers cautioned that finasteride’s potential to blunt some testosterone-mediated effects — particularly those most dependent on DHT, such as certain types of body hair growth — warrants further investigation.

The evidence base here is still thin compared to the literature on cisgender men, and much of the clinical guidance is extrapolated. A review of hair loss treatments in transgender and gender-diverse populations listed finasteride 1 mg daily as a first-line option, alongside topical minoxidil and low-level laser therapy.⁸ If you’re a transgender man considering this combination, the conversation with your endocrinologist should include honest discussion of which masculinizing effects you’re most unwilling to compromise on, since those priorities will influence whether finasteride makes sense for you.

What to Monitor and Expect

If you and your doctor decide to combine testosterone and finasteride, the monitoring schedule generally tracks what you’d already do on TRT, with a few finasteride-specific additions. Testosterone, DHT, estradiol, and PSA levels all shift when the two drugs interact. The spinal cord injury study documented that the combination consistently raised testosterone and estradiol while reducing DHT.⁴ The estradiol increase is worth knowing about because it can occasionally lead to symptoms like breast tenderness, though this is typically manageable with dose adjustment.

PSA interpretation gets trickier on finasteride. The drug roughly halves PSA levels over time, so if your doctor is screening for prostate cancer, they need to account for that suppression — a “normal” PSA on finasteride might actually be elevated if corrected for the drug’s effect. Make sure every provider involved in your care knows you’re taking both medications, because a PSA reading that looks reassuring on paper could mask a clinically meaningful value if the finasteride factor isn’t applied.

One clinical summary put the interaction bluntly: finasteride blocks the actions of DHT that mainly affect the prostate and hair, so testosterone replacement can safely be prescribed alongside it in patients with low testosterone and benign prostate enlargement.¹⁸ “Safely” in this context means the combination has been used in clinical trials lasting up to three years without unexpected adverse events emerging in the combination group that weren’t already known for each drug individually. It does not mean zero risk — both drugs carry their own side effect profiles, and those don’t vanish when you stack them.

Why DHT Matters Less Than People Think

If there’s one theme running through the research, it’s that DHT gets too much credit for testosterone’s positive effects. Study after study has found that blocking DHT with finasteride did not reduce testosterone’s benefits on muscle mass, bone density, fat loss, physical performance, cholesterol levels, or red blood cell production.³ ¹⁰ The tissues where DHT clearly dominates — the prostate, the scalp, the oil glands — are exactly the tissues where you’d often prefer less androgenic stimulation.

That separation is what makes the combination pharmacologically elegant. You’re not working against yourself by taking both; you’re exploiting the fact that different tissues respond to different androgens. The worry that blocking DHT will somehow cancel out your testosterone therapy doesn’t hold up in the clinical data. Where DHT does matter — in mood-regulating neurosteroids, for instance — the effects are subtler, less understood, and affect a smaller number of people. For most individuals, the combination does what it’s supposed to: you keep the benefits of testosterone where you want them and reduce the side effects where you don’t.

1
PubMed Central. Finasteride-its impact on sexual function and prostate cancer
2
The Journal of Clinical Endocrinology & Metabolism. Exogenous Testosterone Alone or with Finasteride Increases Physical Performance, Grip Strength, and Lean Body Mass in Older Men with Low Serum T
3
PubMed Central. Musculoskeletal and prostate effects of combined testosterone and finasteride administration in older hypogonadal men: a randomized, controlled trial
4
Frontiers in Neurology. Musculoskeletal and body composition response to high-dose testosterone with finasteride after chronic incomplete spinal cord injury—a randomized, double-blind, and placebo-controlled pilot study
5
The Journal of Clinical Endocrinology & Metabolism. Exogenous Testosterone or Testosterone with Finasteride Increases Bone Mineral Density in Older Men with Low Serum Testosterone
6
PubMed. Prolonged treatment with finasteride (a 5 alpha-reductase inhibitor) does not affect bone density and metabolism
7
PubMed. Finasteride: a review of its use in male pattern hair loss
8
PubMed. Androgenetic alopecia in transgender and gender diverse populations: A review of therapeutics
9
PubMed Central. The effect of GGC and CAG repeat polymorphisms on the androgen receptor gene in response to finasteride therapy in men with androgenetic alopecia
10
PubMed Central. Testosterone alters iron metabolism and stimulates red blood cell production independently of dihydrotestosterone
11
Oxford Academic (The Journal of Sexual Medicine). Adverse Side Effects of 5α-Reductase Inhibitors Therapy: Persistent Diminished Libido and Erectile Dysfunction and Depression in a Subset of Patients
12
PubMed Central. Post-finasteride syndrome
13
PubMed. Patients treated for male pattern hair with finasteride show, after discontinuation of the drug, altered levels of neuroactive steroids in cerebrospinal fluid and plasma
14
The Journal of Sexual Medicine. Neuroactive Steroid Levels are Modified in Cerebrospinal Fluid and Plasma of Post‐Finasteride Patients Showing Persistent Sexual Side Effects and Anxious/Depressive Symptomatology
15
Actas Dermo-Sifiliográficas. Impact of Finasteride and Dutasteride in Beard Thickness in Men With Androgenetic Alopecia: A 453-patient Retrospective Trial
16
Iraqi Postgraduate Medical Journal. Therapeutic Evaluation of Spironolactone and Finasteride in the Treatment of Acne Vulgaris
17
PubMed Central. The safety and efficacy of finasteride for transgender men with androgenetic alopecia: a case series
18
Endocrine Abstracts. Testosterone replacement in the setting of Finasteride therapy: a therapeutic dilemma