If you’ve researched hair loss, you’ve probably come across the phrase: DHT blocker. It’s become a common shorthand in hair loss discussions and product marketing, often used to describe everything from prescription medications to supplements, shampoos, and botanical blends.
In fact, the term DHT blocker is used so extensively that a quick Internet search makes it difficult to grasp (let alone define) what a DHT blocker even is.
So, what is a DHT blocker, actually? Are all DHT blockers created equal? And most importantly, how does a DHT blocker stop hair loss?
We’ll answer these questions and more in the rest of this DHT blocker article – just continue reading.
What Is DHT and Why Does It Matter for Hair?
DHT stands for dihydrotestosterone, a male hormone – also known as an androgen. It’s produced when an enzyme called 5a-reductase converts testosterone into DHT. Compared to testosterone, it’s a more powerful, potent male hormone.
DHT plays an essential role in male physiology. During fetal development, DHT plays a critical role in male sexual development, and later in life it contributes to prostate growth and maintenance, as well as to facial and body hair growth during puberty.
However, in individuals who are genetically predisposed, DHT exerts the opposite effect at the scalp. Instead of promoting hair growth and thickness (as in the beard and body), it causes balding.
More specifically, DHT binds to androgen receptors in predisposed hair follicles – usually located at the temples and crown – and initiates a cascade of changes that drive progressive follicle miniaturization. This miniaturization is the hallmark process of male pattern baldness, also known as androgenic alopecia (AGA). The involvement of androgens like DHT is where AGA derives its name.
Where Does DHT Come From?
DHT is considered a paracrine hormone. This means that DHT is mostly produced locally within target tissues.
When it comes to hair loss, that means DHT found in the scalp is typically produced in the scalp. In male pattern baldness, DHT levels are elevated in the balding regions of the scalp, compared to non-balding areas. There is also higher activity of 5a-reductase in these areas, the enzyme responsible for producing DHT.
How Does DHT Cause Hair Loss?
DHT is believed to cause hair loss via its influence on hair follicle miniaturization. While we don’t know exactly how DHT contributes to miniaturization, researchers believe it could involve multiple mechanisms:
-
Perifollicular fibrosis: Over time, excess collagen accumulates around the hair follicle, a process known as perifollicular fibrosis. This buildup physically limits hair width, leading to thinning hair shafts over time. DHT may be involved in perifollicular fibrosis via its effects on collagen signaling.
-
Shortening of the growth phase: DHT may play a part in shortening the anagen (growth) phase of the hair cycle. Because follicle miniaturization tends to progress with each successive cycle, faster or prematurely terminated growth phases may accelerate thinning.
-
Dermal papilla shrinkage: The dermal papilla – a specialized cluster of cells at the base of the follicle that regulates hair growth – appears to decrease in size under the influence of DHT. Since the size of the dermal papilla directly influences follicle and hair shaft diameter, its reduction is thought to be a key contributor to progressive follicle miniaturization in pattern hair loss.
The Takeaway: DHT Matters Because It Causes Hair Loss
DHT is a central factor in the development of male pattern hair loss. As a result, addressing the issue of DHT is paramount to slowing, stopping, and reversing patterned hair loss.
This is where DHT Blockers come in.
What Is a DHT Blocker and How Does It Stop Hair Loss?
As mentioned previously, “DHT Blocker” is a broad term. It doesn’t necessarily refer to any compound in particular. Instead, it refers to a benefit that a given compound can have – the ability to block DHT.
From a molecular perspective, DHT can be blocked in two distinct ways:
-
5a-reductase inhibition (most common). This type of DHT blocking involves reducing the activity of the 5α-reductase enzyme that converts testosterone into DHT. There are three isoforms or “types” of 5a-reductase, type I, II, and III. Some DHT blockers target one or more of the types.
-
Androgen receptor blockade. Once DHT is formed, it causes hair loss by binding to the androgen receptor. By blocking DHT from binding to the androgen receptor, DHT can’t exert its effects.
So, broadly, any compound that inhibits the 5a-reductase enzyme and / or blocks the androgen receptor can be considered a DHT blocker.
How Does a DHT Blocker Stop Hair Loss?
As discussed earlier, DHT contributes to male pattern hair loss by progressively shrinking susceptible follicles and shortening the growth phase of the hair cycle, leading to progressive hair thinning.
When DHT binds to androgen receptors within genetically sensitive hair follicles, it triggers a cascade of changes that result in thinner, shorter hairs with each successive growth cycle. DHT blockers reduce this signal – either by lowering the amount of DHT available at the follicle or by limiting its activity.
In short, DHT blockers stop hair loss by interfering with DHT’s ability to participate in the hair thinning process. To be clear, this only applies to AGA and not other forms of hair loss, like telogen effluvium, unrelated to DHT.
However, AGA and telogen effluvium can often occur together, in which case DHT blockers can stop hair loss related to the AGA component.
Finasteride is the most well-studied example of a DHT blocker and provides strong clinical evidence of this DHT-blocking in action. Finasteride is a 5a-reductase inhibitor and specifically inhibits the enzyme's type II isoform – the most relevant type for AGA. By lowering DHT levels, finasteride reduces androgen signaling at vulnerable hair follicles, directly tackling the core driver of male pattern baldness.
Across decades of study, oral finasteride has consistently been shown to slow, stop, and, even partially reverse miniaturization. This not only illustrates the role of DHT in male pattern hair loss, but also that blocking DHT is an effective means of addressing it.
What Are Some Common DHT Blockers?
DHT blockers come in all shapes and sizes. Some are pharmaceutical, others are natural, and the clinical evidence to support their use varies.
Finasteride
Finasteride is the most widely studied and clinically-supported DHT blocker for hair loss.
Used orally, (typically at 1 mg daily) it’s an FDA-approved medication for male pattern hair loss and has decades of clinical data showing it can slow hair loss, stabilize hair density, and promote regrowth. More recently, topical finasteride products have grown in popularity, at concentrations ranging from 0.005% topical finasteride, all the way up to 1%.
As already mentioned, it works by inhibiting a single type of 5a-reductase: the type II isoform.
In its oral form, finasteride inhibits DHT throughout the body, including the scalp. As a result, oral finasteride, dosed at 1 mg daily, typically reduces blood measurements of DHT by upwards of 70%. At the scalp level, 1 mg oral finasteride can reduce DHT by up to 50%.
Topical finasteride, on the other hand, can block scalp DHT by up to 70%, depending on the concentration and daily dosage used.
Dutasteride
Dutasteride is a more potent 5α-reductase inhibitor than finasteride. Unlike finasteride, which inhibits type II 5α-reductase, dutasteride inhibits both type I and type II isforms. As a result, it produces a more profound reduction in serum DHT levels – upwards of 90%.
In published research, dutasteride reliably improves hair counts and seems to be more effective than finasteride (though research is still early). And despite the greater reduction in DHT levels, researchers have observed a similar rate of side effects.
Although dutasteride is similar to finasteride and FDA-approved for a condition called benign prostatic hyperplasia (BPH), it is often used off-label for hair loss. The most commonly reported dose in research is 0.5 mg per day, which one study found led to a 51% reduction in scalp DHT levels.
Like finasteride, dutasteride has also been used in topical form. In one study, topical dutasteride at 3 different concentrations – 0.01%, 0.02%, and 0.05% – was more effective than oral finasteride (1 mg). And while oral finasteride and 0.05% dutasteride did reduce blood levels of DHT, 0.01% and 0.02% topical dutasteride had no appreciable impact on DHT levels.
Dutasteride also seems to be an alternative for those resistant to finasteride. In one study, 0.5 mg of dutasteride daily increased hair counts in participants who had previously tried finasteride without success.
At ulo, we offer the ability to elect both oral and topical dutasteride as a preference in your consultation with an ulo-partnered physician. If prescribed, your medication will be delivered discreetly to your doorstep.
Unlike other telemedicine platforms, we never compound our oral dutasteride with other medications like minoxidil. Instead, we follow the evidence – only ever offering dutasteride in its clinically-studied, fully-emulsified softgel form.
Ketoconazole
Ketoconazole is an antifungal medication commonly used in medicated shampoos for dandruff and seborrheic dermatitis. While not a primary DHT blocker, studies show that ketoconazole demonstrates a mild inhibitory effect on 5a-reductase. It also blocks the androgen receptor, offering a dual DHT blocker effect.
Beyond its function as a DHT blocker, It also offers anti-inflammatory effects and helps maintain a healthier scalp environment.
Saw Palmetto
Saw palmetto (Serenoa repens) is one of the most well-known natural DHT blockers and the most well-studied extract for natural hair growth. Studies show saw palmetto extract blocks DHT by inhibiting 5a-reductase and impacting the function of the androgen receptor, attributed to its fatty acid content.
From a clinical perspective, studies examining the effectiveness of saw palmetto have seen positive results.
In one 2012 study, while only 38% of participants using saw palmetto for hair loss experienced an increase in hair growth, 90% of participants saw hair loss stabilization – in other words, their hair loss stopped. Comparatively, 68% of participants taking oral finasteride experienced hair regrowth. Both groups experienced minimal side effects.
In another study, both topical and oral formulations of saw palmetto led to a marked reduction in hair fall and a 5-7% increase in hair counts. While no change in blood levels of DHT was observed with the topical formulation, the oral formulation reduced serum DHT levels by 1.29-fold.
Most recently, a 2025 study exploring the efficacy of a standardized saw palmetto extract found a significant improvement in hair counts in both men and women with self-perceived hair thinning.
Overall, saw palmetto is a weaker overall DHT blocker compared to DHT-blocking medications. However, research suggests it can still have a significant impact on DHT and hair growth in AGA. Due to its natural origin, it may be a better fit for those with a preference for natural DHT blockers.
But, it’s important to note: the type of extract matters. Like all natural products, the composition of the extract can vary depending on harvest time, growing season, growing conditions, and more.
Because of this, the efficacy of a natural DHT blocker like saw palmetto can fluctuate substantially from batch to batch – simply because the compounds that make up the extract can have so much natural variation.
That’s why when you’re looking for a high quality saw palmetto supplement, you should always opt for standardized extracts.
Our Hair Growth Supplement leverages a saw palmetto extract standardized to 85% fatty acids – the active compounds responsible for DHT inhibition, for a reliable approach to natural hair growth.
For those that prefer topical application, our Hair Growth Serum also boasts 2% saw palmetto, alongside clinically-studied complexes Redensyl™, Capixyl™, and Procapil™, for targeted natural support. For maximal gains, we recommend combining the two.
Beta Sitosterol
Beta-sitosterol is a plant-derived phytosterol, known for its anti-inflammatory effects.
Studies show it demonstrates some DHT blocking effects, attributed to its ability to block 5a-reductase activity. Like ketoconazole, research suggests it exhibits dual DHT blocking capabilities – the ability to block DHT from binding to androgen receptors.
According to clinical research, beta-sitosterol may help improve hair growth when combined with saw palmetto. In one study, the combination of the two resulted in improved hair growth for 60% of participants.
Our Hair Growth Supplement combines standardized saw palmetto with beta-sitosterol, derived from Phytopin Pine to optimize natural growth.
Astaxanthin
Astaxanthin is a brightly-colored carotenoid with strong antioxidant and anti-inflammatory properties. Studies show it has DHT-blocking capacity, as evidenced by its ability to block 5a-reductase activity. Moreover, when combined with saw palmetto, it results in better DHT inhibition than saw palmetto alone.
While astaxanthin hasn’t been studied on its own in hair loss, one study that tested a supplement blend of saw palmetto, astaxanthin, and maca root found improved hair growth in peri-, post-menopausal, and menopausal women with thinning hair. However, the study didn’t specify a hair loss diagnosis – just generalized thinning. This means we can’t necessarily pin down whether these improvements are due to DHT blocking or another mechanism.
Are DHT Blockers Safe?
When looking at the safety of compounds that block dihydrotestosterone (DHT), the most reliable data we have comes from oral finasteride. It’s the best-studied DHT-lowering therapy to date, with decades of randomized trials, post-marketing surveillance, and large observational studies.
Consequently, it’s the primary reference point for understanding both the benefits and risks of DHT blockers.
DHT Blocker Side Effects: What Finasteride Can Tell Us
Across clinical trials, oral finasteride is generally well tolerated, with most men experiencing no adverse effects. When side effects do occur, they are typically related to sexual function (e.g., reduced libido or erectile dysfunction), mood, or cognition, and affect a small percentage (less than 2%) of users.
When side effects do occur, they are believed to arise from systemic DHT reduction. This distinction matters, because it helps explain how the route of administration impacts risk of side effects.
Oral vs. Topical DHT Blockers
Oral DHT blockers reduce DHT throughout the entire body, including tissues where DHT serves physiological roles beyond hair, such as the central nervous system.
In contrast, topical DHT blockers are designed to focus DHT suppression to the scalp. They target the exposure to the hair follicle while limiting how much active compound reaches the bloodstream.
In theory, lower systemic exposure should result in less systemic DHT impact, thereby lowering the risk of side effects. This is the main rationale for using topical finasteride.
However, even with topical application, dose still matters. In some studies, topical application of finasteride still resulted in comparable reductions of systemic DHT, attributed to the dose used in the study:
-
1 mL of 0.25% topical finasteride, equating to 2.275 mg of finasteride, applied daily, lowered serum DHT to the same degree as 1 mg oral finasteride.
-
Another study found a daily dose 0.05 to 0.2 mL of 0.25% topical finasteride, equating to 0.1 to 0.6 mg finasteride, lowered serum DHT by 34.5% versus 55.6% in the oral finasteride group.
-
The minimum effective dose seems to be 0.005% topical finasteride, which one study found had negligible impacts on blood levels of DHT while still improving hair counts in men with AGA.
These results also seem to translate to natural DHT blockers like saw palmetto.
As mentioned earlier, topical application of saw palmetto improved hair counts with no appreciable impacts to blood measurements of DHT, whereas oral administration reduced blood DHT by 1.29-fold. Although saw palmetto is a comparatively weaker DHT inhibitor than finasteride and studies on saw palmetto have observed minimal side effects, the principle still applies.
Dutasteride also follows a similar trend: while higher concentrations seem to have a more pronounced impact on serum DHT, lower concentrations from 0.01-0.02% have minimal impact on systemic DHT levels.
The Impact of Molecular Weight on Side Effects of DHT Blockers
The molecular weight of compounds play an important role in how our body utilizes them and, as a result, how they interact with different tissues in the body.
When it comes to side effects, this matters, especially when comparing finasteride and dutasteride.
Finasteride’s impact on the brain is one significant factor that researchers believe could be involved in the risk of side effects. The drug reaches the brain via crossing the protective barrier around the brain, called the blood brain barrier (BBB).
The permeability of the blood brain barrier to compounds like finasteride is, in part, determined by molecular weight. Compounds with a molecular weight over 400 Daltons typically have a harder time penetrating the BBB and, as a result, reaching the central nervous system.
So, how does this relate to finasteride and dutasteride?
Finasteride has a molecular weight of 372.55 Da whereas dutasteride has a molecular weight of 528.5 Da. This means, in comparison, dutasteride likely has a harder time reaching the brain. In theory, this could translate to a lower risk of side effects when compared to finasteride due to lower exposure to the central nervous system.
The overall research suggests a similar rate of side effects between finasteride and dutasteride – this is despite the fact that dutasteride is much more effective at inhibiting DHT. Moreover, specific studies have found a significantly higher rate of side effects with finasteride than dutasteride. Altogether, this points to dutasteride’s unique profile having a distinctly different impact to the body, despite its mechanistic similarity to finasteride.
Side Effects of DHT Blockers: The Takeaway
In sum total, there is a low risk of side effects when using a DHT blocker. However, like with any treatment, those risks are not zero. Nonetheless, there are strategies available to reduce even the low risk of side effects.
What Is The Best DHT Blocker?
There’s no single “best” DHT blocker for everyone. But, there is a clear starting point: finasteride.
While it would be reductionist to label finasteride as the best DHT blocker, it is the most thoroughly studied DHT blocker available. It has decades of clinical data, multiple randomized controlled trials, and long-term safety monitoring supporting its ability to slow, stop, and, in some cases, reverse pattern hair loss in men.
From a purely evidence-based standpoint, finasteride remains the gold standard against which all other DHT-blocking therapies are measured.
That said, the best DHT blocker isn’t necessarily the one with the most data. Instead, your selection should also be informed by what best fits your goals, risk tolerance, and lifestyle:
-
If your priority is using treatments backed by the strongest clinical evidence, oral finasteride should be at the top of your list. Its effects on scalp DHT and hair growth are well characterized and consistently associated with improved hair outcomes in male pattern baldness.
-
If you’re more risk-averse or concerned about systemic DHT suppression, a topical DHT blocker may be a better fit. Options to consider may include low-dose topical finasteride, which aims to reduce DHT locally at the scalp while limiting systemic exposure, or natural blockers like saw palmetto or beta-sitosterol. While these approaches generally have less robust data than oral finasteride, they may offer a more comfortable balance between efficacy and tolerability for some individuals – especially if your priority is to avoid systemic impacts to DHT.
-
If you’re open to newer therapies, discuss dutasteride with a board-certified practitioner. Dutasteride produces greater DHT suppression than finasteride and may have a similar rate of side effects, according to available research. Although it’s not FDA-approved for hair loss, it is sometimes prescribed off-label.
-
If convenience is a deciding factor, oral options may be preferable. A once-daily pill – whether finasteride, dutasteride (off-label), or even a supplement like saw palmetto – can be easier to maintain consistently than a topical routine.
In short, finasteride is the DHT blocker with the most evidence to support its use. But the “best” DHT blocker is ultimately one that suits your comfort around systemic exposure, your tolerance for side effects, your lifestyle, and your ability to stay consistent over time.
Can You Combine DHT Blockers With Other Hair Loss Treatments?
DHT blockers are often combined with other non-hormonal modalities. For example, finasteride and minoxidil, a vasodilator and growth promoter, are often used together for better results.
Studies show that the topical combination of finasteride and minoxidil is more effective for male pattern hair loss than either minoxidil or finasteride alone. As a result, combination therapies reflect a more aggressive approach to addressing hair loss.
ulo’s personalized approach puts you in control of your protocol. That’s why we offer combination finasteride and minoxidil in both topical and oral forms.
DHT Blocker FAQs
Do DHT blockers work for everyone with hair loss?
No, DHT blockers should only be used for pattern hair loss. A diagnosis can help you decide whether a DHT blocker could be useful.
Do I have to use a DHT blocker forever?
Pattern hair loss is usually progressive. If you stop a therapy that was helping, hair typically trends back toward baseline over time.
Are natural DHT blockers enough on their own?
Research suggests natural DHT blockers like saw palmetto have the ability to stabilize hair loss and promote hair growth. However, individual results will vary.
Can women use DHT blockers?
While women of childbearing age should not use finasteride or dutasteride, some practitioners do prescribe DHT blockers to postmenopausal women.
Are DHT blockers dangerous?
According to clinical research on finasteride, the risk of side effects are low (less than 2%). However, they should always be used under the guidance of a physician.
The Verdict: DHT Blockers Stop Hair Loss, But Context Matters
DHT blockers play a central role in the treatment of pattern hair loss (AGA) because they target one of its primary biological drivers: DHT-mediated follicle miniaturization. Decades of research on finasteride have demonstrated that reducing DHT can slow, stop, and, in some cases, partially reverse patterned hair loss.
At the same time, the term “DHT blocker” encompasses a broad spectrum of compounds with very different mechanisms, strengths of evidence, and safety profiles:
-
Oral finasteride remains the most thoroughly studied and reliable treatment.
-
Topical formulations, like topical finasteride, aim to preserve efficacy while reducing systemic exposure.
-
Botanical agents such as saw palmetto and beta-sitosterol may offer natural growth enhancement, through their modulation of DHT pathways.
Examining the research on DHT blockers overall, there is no universally “best” DHT blocker. The most appropriate choice hinges on your diagnosis, your tolerance for systemic DHT suppression, your comfort with risk, and your ability to remain consistent over time.
For some, oral finasteride offers the most reliable, evidence-based path. For others, a topical or lower-dose approach may better fit their priorities. And for individuals exploring alternatives, natural DHT modulators may serve a supportive role.
Hair loss treatment isn't about chasing absolutes. Instead, it’s about selecting a strategy that fits both your hair loss and the realities of your life. With a clear understanding of what DHT blockers are, how they stop hair loss, what the evidence supports, and where trade-offs exist, you’re better positioned to make informed decisions alongside a qualified healthcare provider.
At ulo, we believe effective treatment starts with you – your preferences, your journey, your protocol. Under the guidance of board-certified physicians, we offer a wide array of solutions to help you address your hair loss, your way. Explore DHT blockers like low dose topical finasteride (starting at $49/month), oral finasteride (starting at $24/month), or saw palmetto, found in our Hair Growth Serum, Hair Growth Supplement, and Thickening Shampoo. Plus, get 24/7 access to our physician network with every Rx purchase.
Disclaimer: Hair health is personal. This article is meant to help you understand published research, but it’s not a substitute for medical advice, diagnosis, or treatment. For guidance tailored to your needs, speak with a licensed healthcare provider who can evaluate your unique health and goals.
*Prescription products require a medical evaluation with a medical provider who will determine if a prescription is appropriate. This medical evaluation is included in the cost at checkout. See our website for important safety information.