Does finasteride affect morning wood? Understanding the side effects

October 7, 2025 •

4 min read

While regular morning erections (nocturnal penile tumescence) are often a sign of healthy erectile function, many men report a decrease or loss of them while on finasteride. Clinical data reveals that a small percentage of men taking finasteride for hair loss experience erectile dysfunction, a side effect that can include the loss of spontaneous nighttime and morning erections.

Quick Summary

Finasteride can cause erectile dysfunction and loss of morning erections by lowering dihydrotestosterone (DHT) levels. While uncommon at lower doses for hair loss, this is a documented side effect that may reverse upon discontinuing the medication, though some report persistent symptoms.

Key Points

Finasteride can reduce morning wood: Finasteride may decrease or cause the loss of morning erections by inhibiting DHT, a hormone important for erectile function.
Effect is typically uncommon at 1mg dose: For men taking the 1mg dose for hair loss, sexual side effects like erectile dysfunction, which includes loss of morning wood, are relatively rare.
Higher risk with higher dosage: The 5mg dose used for benign prostatic hyperplasia (BPH) is associated with a significantly higher risk of sexual side effects.
Reversibility is common: For most men, finasteride's sexual side effects are temporary and will resolve after discontinuing the medication.
Post-Finasteride Syndrome is a risk: In rare cases, some men experience persistent sexual dysfunction, known as Post-Finasteride Syndrome, even after stopping the drug.
Morning wood indicates health: A decrease in morning wood can signal an underlying health issue, not necessarily caused by finasteride, such as vascular problems or hormonal imbalances.
Psychological factors play a role: The 'nocebo effect', where a person's negative expectations of side effects increase their likelihood, can contribute to reported sexual dysfunction.
Consult a doctor: If you experience loss of morning wood, talk to a healthcare provider to explore potential causes and treatment options.

The Link Between Finasteride and Morning Erections

Morning wood, clinically known as nocturnal penile tumescence (NPT), is a natural phenomenon where men experience involuntary erections during sleep, typically during the REM phase. A consistent presence of NPT is widely regarded as a good indicator of healthy penile blood flow and functioning nerves. Therefore, a noticeable decrease or complete absence of these erections is a potential red flag for underlying erectile issues.

Finasteride's mechanism of action involves inhibiting the enzyme 5-alpha-reductase, which is responsible for converting testosterone into the more potent androgen, dihydrotestosterone (DHT). While this process is effective for treating male pattern baldness (androgenetic alopecia) by reducing the DHT that shrinks hair follicles, it also lowers DHT levels throughout the body. DHT is involved in a range of functions, including the maintenance of libido and proper erectile function, particularly through its role in producing nitric oxide in the penis. By reducing DHT, finasteride can inadvertently interfere with the hormonal and neurological signaling necessary for firm erections.

How Prevalent are the Side Effects?

Clinical trials and post-marketing reports present conflicting data on the frequency of sexual side effects from finasteride, which has fueled controversy.

Hair Loss Dose (1mg)

Initial Trials: Early FDA-controlled clinical trials found low rates of sexual side effects. For example, in a one-year trial for male pattern baldness, 1.3% of men on finasteride reported erectile dysfunction compared to 0.7% on placebo. Other issues like decreased libido (1.8%) and ejaculation problems (1.2%) were also reported at low rates.
Long-Term Data: Some long-term studies suggest that side effects may decrease over time, with one report indicating ED rates dropped to under 0.3% by the fifth year of treatment.

BPH Dose (5mg)

Higher Risk: The higher 5mg dose used for benign prostatic hyperplasia (BPH) is associated with a greater risk of sexual side effects. Meta-analyses of BPH trials have shown significantly higher risks of ED and reduced libido compared to placebo.
Age Factor: Men taking finasteride for BPH are typically older and already have a higher baseline risk for erectile dysfunction due to age and comorbidities, which can confound the data.

Factors Influencing Finasteride Side Effects

Several factors can influence the likelihood and severity of experiencing sexual side effects while on finasteride, including the loss of morning wood.

Dose: The higher 5mg dose for BPH carries a higher risk of side effects than the 1mg dose for hair loss.
Age: Older men are generally more susceptible to sexual side effects, partly due to the normal age-related decline in testosterone levels and increased risk of cardiovascular issues.
Nocebo Effect: Awareness of potential sexual side effects can increase their reported incidence. Some studies suggest that patients informed about these risks are more likely to report them than those who are not counseled.
Individual Sensitivity: A person's unique metabolic response to finasteride and sensitivity to changes in DHT and neurosteroids can affect how they experience side effects.
Psychological Factors: Anxiety, depression, and stress can contribute to erectile dysfunction and may be exacerbated by concerns over sexual performance.

Comparison of Finasteride 1mg vs. 5mg Sexual Side Effects

This table summarizes the key differences in reported sexual side effects based on finasteride dosage.


Side Effect	Finasteride 1mg (Androgenetic Alopecia)	Finasteride 5mg (Benign Prostatic Hyperplasia)
Erectile Dysfunction	Low incidence (~1.3% in early trials)	Higher incidence (rates vary, up to 15-18% reported)
Decreased Libido	Low incidence (~1.8% in early trials)	More frequently reported than with the 1mg dose
Ejaculation Disorders	Low incidence (~1.2% in early trials)	More frequently reported, especially reduced volume
Age at Risk	Typically younger men (20s-40s)	Typically older men (50+)
Duration of Use	Effects may decrease over time for many users	Effects more persistent or worsening with long-term use in some

What to Do if You Lose Morning Wood

If you've noticed a significant change in your morning erections while on finasteride, it is essential to consult a healthcare provider. They can help determine the cause and discuss the best course of action.

Assess Other Factors: Review your lifestyle for contributing issues such as stress, poor sleep, alcohol intake, or other medications.
Rule Out Other Conditions: A doctor can screen for other health problems that cause ED, such as cardiovascular disease, diabetes, or hormonal imbalances.
Consider Medication Adjustment: Your doctor may recommend adjusting your finasteride dose or timing.
Explore Alternative Treatments: Discuss other hair loss treatments like topical minoxidil or topical finasteride, which may have fewer systemic side effects.
Stop the Medication: In many cases, sexual side effects resolve after discontinuing finasteride. Your doctor can help you with this decision. Please do not stop the medication abruptly without consulting your healthcare provider..

Post-Finasteride Syndrome (PFS)

In rare cases, a small percentage of men report persistent sexual and nonsexual side effects that continue for three months or more after stopping finasteride. This is known as Post-Finasteride Syndrome (PFS), a controversial and not fully understood condition. While research is ongoing, documented cases describe symptoms including long-term ED, decreased libido, and neuropsychiatric issues. Men who experience persistent symptoms should seek specialized medical evaluation.

Conclusion

While finasteride is a widely used and generally well-tolerated medication, it does carry a risk of sexual side effects, including the loss of morning wood. This effect is generally uncommon, especially at the 1mg dose for hair loss, and often reversible upon discontinuation. The mechanism is believed to involve the medication's impact on DHT, a hormone critical for sexual function. If you experience this side effect, it's crucial to consult with your doctor to rule out other potential causes and discuss the best course of action for your individual health. The existence of persistent symptoms in a small number of men (PFS) highlights the importance of thorough patient counseling on the potential risks before starting treatment.

An extensive review of the conflicting data on finasteride and erectile dysfunction can be found in the World Journal of Men's Health(https://wjmh.org/DOIx.php?id=10.5534/wjmh.180029).

Frequently Asked Questions

Yes, finasteride can cause a complete loss of morning wood, or nocturnal penile tumescence, in some individuals. While this is not a universal experience and is relatively uncommon at the 1mg dose, it is a documented sexual side effect related to the drug's action on DHT.

A persistent loss of morning wood can be a sign of erectile dysfunction (ED), as it indicates a potential issue with hormonal or vascular function. However, a healthcare provider should perform a full evaluation, as many factors beyond finasteride can cause ED, including stress, other medical conditions, and psychological factors.

In most cases, sexual side effects from finasteride, including the loss of morning wood, are reversible. Many men experience a return to normal sexual function after discontinuing the medication, often within a few weeks. However, some rare cases of persistent symptoms have been reported.

Yes, the higher 5mg dose of finasteride used for benign prostatic hyperplasia (BPH) is associated with a significantly higher rate of sexual side effects, including erectile dysfunction and decreased libido, compared to the 1mg dose for hair loss.

NPT, or morning wood, occurs involuntarily during sleep and indicates healthy physical function, particularly blood flow. Psychologically-induced erections, on the other hand, are triggered by mental arousal and can help distinguish physical from psychological ED, as men with purely psychological ED may still experience NPT.

Yes, it is possible. The 'nocebo effect' is a phenomenon where negative expectations about a drug's side effects can actually lead to their occurrence. Stress and performance anxiety can also contribute to erectile issues independent of the drug's physiological effects.

You should not stop taking finasteride without consulting your healthcare provider. While many side effects subside after discontinuing the drug, a doctor can help you weigh the risks and benefits, investigate other potential causes, and discuss alternative treatment options.