What happens if you take testosterone and finasteride together?

October 7, 2025 •

4 min read

One study involving men on high-dose TRT and finasteride found significant improvements in body composition and muscle strength without the prostate enlargement typically associated with testosterone alone. This highlights why many people ask, 'what happens if you take testosterone and finasteride together?' as they navigate hormone therapy.

Quick Summary

Combining testosterone and finasteride therapy blocks the conversion of testosterone to DHT, allowing for testosterone replacement therapy's benefits while mitigating specific side effects like hair loss and prostate enlargement. This medical strategy requires careful oversight and regular monitoring.

Key Points

Blocking DHT: Finasteride inhibits the enzyme that converts testosterone to dihydrotestosterone (DHT), effectively lowering DHT levels while on TRT.
Mitigating Hair Loss: The combination is used to prevent or reduce male pattern baldness that can be exacerbated by increased testosterone levels from TRT.
Protecting Prostate Health: Finasteride helps prevent prostate enlargement (BPH), a potential side effect of TRT, by reducing DHT's proliferative effect on prostate tissue.
Hormone Level Monitoring: Combining these medications requires regular monitoring of testosterone, DHT, and estrogen levels due to the altered hormone balance.
Managing Side Effects: Patients may experience sexual side effects (e.g., decreased libido, erectile dysfunction) and should discuss these with their doctor, as the root cause may be reduced DHT rather than lowered testosterone.
Medical Supervision is Crucial: This treatment approach should always be managed by a qualified healthcare provider to ensure safety and effectiveness.

The Hormonal Dance: How Testosterone and Finasteride Interact

Understanding the combined effects of testosterone and finasteride begins with their distinct roles in the body's hormonal system. Testosterone is the primary male sex hormone, responsible for characteristics like muscle mass, libido, and bone density. A percentage of this testosterone is converted into a more potent androgen called dihydrotestosterone (DHT) by the enzyme 5-alpha-reductase. While DHT is essential for some developmental functions, it is also responsible for specific unwanted effects in adulthood.

Finasteride is a 5-alpha-reductase inhibitor, meaning it blocks the enzyme that facilitates this conversion. By doing so, it significantly lowers the amount of DHT circulating in the body, while the amount of unconverted testosterone may temporarily increase. In a standalone context, this action is the basis for finasteride's use in treating male pattern baldness and benign prostatic hyperplasia (BPH). When introducing supplemental testosterone through Testosterone Replacement Therapy (TRT), the total testosterone levels are elevated. This, in turn, can lead to a corresponding increase in DHT production. The combination of finasteride with TRT is a strategic choice to manage this rise in DHT, thereby retaining the benefits of TRT while counteracting DHT-specific side effects.

Strategic Reasons to Combine Testosterone and Finasteride

Physicians may recommend taking testosterone and finasteride together for two primary reasons:

Preventing Hair Loss: Individuals on TRT, particularly those with a genetic predisposition, may experience accelerated hair thinning or male pattern baldness due to increased DHT levels. By inhibiting 5-alpha-reductase, finasteride reduces the DHT that affects scalp hair follicles, helping to slow down or prevent this hair loss.
Managing Prostate Health: As men age, the prostate gland can enlarge, a condition known as benign prostatic hyperplasia (BPH). This growth is driven by DHT. Since TRT can stimulate prostate growth, a combined therapy with finasteride can effectively limit this enlargement and alleviate associated urinary symptoms.

The Combined Effects on the Body

When combining these medications, the hormonal profile of a person shifts in several ways, often requiring close monitoring.

Hormone Level Changes:
- Testosterone: The overall testosterone level will be higher due to the TRT. While finasteride alone can cause a slight, temporary increase in T levels, when combined with TRT, the testosterone increase from the replacement therapy is the dominant factor.
- Dihydrotestosterone (DHT): Finasteride dramatically lowers serum DHT levels, significantly offsetting the rise in DHT that would otherwise occur from TRT alone.
- Estrogen: With less testosterone being converted to DHT, more is available for conversion to estradiol (a type of estrogen) through the aromatase enzyme. This can result in increased estrogen levels, which a doctor will monitor to prevent potential side effects like gynecomastia.
Physical Effects:
- Body Composition: Studies indicate that combining TRT and finasteride can increase lean body mass and muscle strength.
- Hair and Skin: The combination helps prevent scalp hair loss triggered by high DHT from TRT. Reduced DHT can also affect skin oiliness and acne, but responses vary.
- Prostate: Finasteride works to prevent the prostate enlargement that can occur with TRT, helping to manage or avoid BPH symptoms.

Managing Expectations and Potential Side Effects

Like any medication regimen, combining testosterone and finasteride can lead to side effects. Patients must have open communication with their healthcare provider to manage expectations and address any issues. Regular blood work is essential to monitor testosterone, DHT, and estrogen levels and make necessary adjustments to dosages.

Potential Side Effects:

Sexual Side Effects: Reduced libido, erectile dysfunction, and decreased ejaculatory volume have been reported with finasteride use, even on TRT. While changes in testosterone levels may not be the cause, the reduction in potent DHT is suspected to play a role.
Gynecomastia: The potential rise in estrogen levels can sometimes lead to the development of breast tissue.
Mental Health: Anxiety and depression are potential side effects associated with finasteride, though some studies suggest combining it with testosterone may affect the risk.

Addressing Concerns:

Comprehensive Monitoring: Regular lab testing and follow-up with a doctor are non-negotiable for anyone on this combination therapy.
Dosage Adjustment: Your doctor may adjust the dose of finasteride or TRT based on your hormone levels and symptom response.
Topical Finasteride: In some cases, topical finasteride may be used to target hair loss more directly while minimizing systemic side effects.

Combination Therapy vs. Monotherapy


Feature	Testosterone Monotherapy	Combination Therapy (Testosterone + Finasteride)
Hormone Profile	Increased Total T, Increased DHT	Increased Total T, Decreased DHT
Effect on Hair	Potential acceleration of hair thinning	Mitigated hair thinning/loss due to lower DHT
Effect on Prostate	Potential for prostate enlargement (BPH)	Reduced risk of prostate enlargement
Sexual Function	Improved libido, potentially improved erectile function	Possible reduced libido, ED, and ejaculatory volume
Monitoring Needs	Requires monitoring of T levels and prostate health	Requires comprehensive monitoring of T, DHT, and estrogen
Side Effect Risk	Less risk of finasteride-specific side effects	Added risk of finasteride-related side effects
Overall Goal	Address low testosterone symptoms	Address low T symptoms while proactively managing DHT-related side effects

Conclusion

Taking testosterone and finasteride together is a viable and often necessary strategy for individuals on Testosterone Replacement Therapy who want to prevent or mitigate specific DHT-related side effects such as male pattern baldness and benign prostatic hyperplasia. While the combination successfully manages these issues by significantly lowering DHT levels, it does introduce a new set of considerations. Potential side effects like changes in sexual function and hormonal shifts, including increased estrogen, necessitate close medical supervision and regular monitoring. By understanding the roles of each medication and working closely with a healthcare provider, patients can balance the benefits of TRT with the protective effects of finasteride, leading to a more complete and safe hormonal therapy experience.

For more detailed pharmacological information on finasteride, you can consult resources from the National Center for Biotechnology Information (NCBI).

Frequently Asked Questions

Yes, taking finasteride and TRT together is common and generally considered safe under medical supervision. This approach is often used to mitigate specific side effects of testosterone therapy, such as hair loss and prostate issues.

No, finasteride will not cancel out the overall effects of testosterone. It works by blocking the conversion of testosterone to DHT, a more potent androgen responsible for specific effects like hair loss. The rest of your body's testosterone will still provide the desired benefits of TRT, such as increased muscle mass and libido.

No, studies show that finasteride does not significantly lower total testosterone levels over the long term, and when combined with TRT, overall testosterone levels will still be elevated. The body compensates for the blocked conversion to DHT, often causing a slight initial rise in testosterone that typically normalizes.

Some potential sexual side effects include decreased libido, erectile dysfunction, and reduced ejaculatory volume. It's important to differentiate these from symptoms of low testosterone, as they are likely related to the reduction in DHT.

By blocking the conversion of testosterone to DHT, finasteride helps prevent prostate enlargement (BPH) that can occur with TRT. In this context, it is used to manage prostate size and associated urinary symptoms.

Yes, it is possible for estrogen levels to increase because more testosterone is available for conversion to estrogen. Your doctor will monitor this and may prescribe an aromatase inhibitor if necessary to keep your estrogen levels in a healthy range.

For managing hair loss specifically, some clinics recommend topical finasteride to target the scalp directly and potentially reduce systemic side effects associated with the oral version. The best option depends on your individual needs and should be discussed with your doctor.