Can You Test DHT Levels? How Testing Works & What Results Mean

DHT, or dihydrotestosterone, can be measured through a standard blood test ordered by a doctor or, in some cases, through direct-to-consumer lab services. Most labs measure DHT using either an immunoassay or a more precise method called liquid chromatography-tandem mass spectrometry. The test itself is straightforward, but interpreting the result is where things get complicated. Serum DHT levels often tell you less than you’d expect about what’s actually happening in your hair follicles, prostate, or skin, and the number on your lab report can vary dramatically depending on which method the lab used.

How DHT Blood Tests Work

The enzyme 5-alpha-reductase converts testosterone into DHT, a more potent androgen that drives processes in the skin, hair follicles, and prostate.¹ When you get a DHT blood test, a sample of your blood is drawn and sent to a lab, which measures the concentration of DHT circulating in your serum. What matters is the method the lab uses to do this, because the two major approaches can produce meaningfully different numbers.

The older and more common method is radioimmunoassay (RIA), which uses antibodies designed to bind to DHT. The problem is that these antibodies aren’t perfectly selective. Other substances in the blood can also bind to them, artificially inflating the result. When researchers compared RIA results to those from LC-MS/MS, a more modern technique that physically separates and identifies individual molecules, DHT readings from immunoassays came back consistently higher.² The gap between the two methods was especially large at low DHT concentrations, exactly the range where you’d want the most precision, such as in women or in men taking medications that suppress DHT.³

Adding a purification step (a chromatographic cleanup before running the immunoassay) narrowed the difference, confirming that the inflated immunoassay numbers were caused by interfering substances rather than actual DHT.² In practice, this means that if you’re comparing your DHT result to a reference range, you need to know whether the range was established using the same method your lab used. A number from an immunoassay and a number from mass spectrometry aren’t directly comparable.

What Your Blood Level Actually Reflects

This is where many people run into a wall. You get a DHT result, it falls within or outside the reference range, and you assume it tells you something definitive about what’s going on in your scalp or prostate. But the relationship between the DHT floating around in your bloodstream and the DHT operating inside target tissues is surprisingly weak.

A detailed review in Endocrine Reviews laid this out clearly: intracellular concentrations of androgens in androgen-sensitive tissues are essentially independent of circulating levels.⁴ In other words, the DHT inside your hair follicles or prostate cells is produced locally by 5-alpha-reductase working on testosterone right there in the tissue. The serum level is more like an echo of total body production than a direct readout of what’s happening at the sites that matter most. This disconnect helps explain why two men with identical blood DHT levels can have very different degrees of hair loss or prostate enlargement.

The review also noted that the success of 5-alpha-reductase inhibitors (drugs like finasteride and dutasteride) in treating conditions like benign prostatic hyperplasia has actually contributed to a misconception that circulating DHT is the key driver of androgenic action in those tissues.⁴ In reality, the drugs work because they block the enzyme inside the tissues, not because they lower the number on a blood test.

Reference Ranges and Why They Shift

If you search for a “normal” DHT range, you’ll find numbers all over the place. Part of this is the assay method issue described above. Part of it is that DHT levels vary by sex, age, and even where someone is in their menstrual cycle.

In women, serum DHT levels stay relatively stable across the menstrual cycle, even as total testosterone rises during the follicular phase and peaks at midcycle. The ratio of DHT to testosterone is roughly 1:4 in women but about 1:13 in men, reflecting the fact that women convert a larger fraction of their circulating testosterone into DHT.⁵ In men, DHT levels tend to rise through puberty, plateau in adulthood, and may shift in older age, though the trajectory is less tidy than for testosterone.

Because of these variables, any single DHT measurement is a snapshot. Labs typically report sex-specific reference ranges, but those ranges were built using a specific assay and a specific population, so always check whether your lab’s range was generated using mass spectrometry or immunoassay. A result flagged “high” on one method could look normal on the other.

The Testosterone-to-DHT Ratio

Sometimes the raw DHT number matters less than its ratio to total testosterone. This ratio shows up in two very different clinical contexts.

In genetic disorders of sexual development, specifically 5-alpha-reductase type 2 deficiency, the testosterone-to-DHT ratio is a primary diagnostic tool. Children and adolescents with this condition can convert testosterone poorly or not at all, so the ratio runs high. Researchers have identified rough cutoffs for the stimulated testosterone-to-DHT ratio at different developmental stages: about 8.5 or higher during minipuberty, 10 or higher before puberty, and 17 or higher during puberty.⁶ Even with these thresholds, the ratio isn’t perfect. In a small case series, half of the patients who had DHT measured didn’t reach the expected diagnostic cutoff.⁷ Genetic testing remains the definitive confirmation.

In women’s health, the testosterone-to-DHT ratio has been studied in polycystic ovary syndrome (PCOS). Research found that women with oligomenorrhea or amenorrhea had a higher ratio than those with regular periods. Interestingly, the ratio also correlated with insulin resistance and fasting blood sugar, while DHT levels alone did not differ between insulin-resistant and non-insulin-resistant groups.⁸ DHT levels did correlate with BMI in that study, suggesting the ratio and the raw level each capture different aspects of what’s going on metabolically.

DHT Testing for Hair Loss

If you’re losing your hair and wondering whether a DHT test will explain the situation, the honest answer is: probably not. This is one of the most common reasons people seek DHT testing, and one of the areas where the test is least informative.

In a study specifically designed to evaluate DHT’s usefulness in diagnosing androgenetic alopecia, researchers found that increased serum DHT concentrations did not correlate with the severity of hair loss.⁹ A separate study looking at young men with androgenetic alopecia confirmed the same pattern: while DHT and free testosterone were higher overall in the hair-loss group compared to controls, there were no significant differences in hormone levels among men with mild, moderate, and severe hair loss.¹⁰ The researchers concluded that hair loss severity was more likely determined by how long the condition had been progressing and by the sensitivity of individual hair follicles to androgens, not by how much DHT was in the blood.

This makes sense given the tissue-versus-serum disconnect. The follicle-level conversion of testosterone to DHT and the density of androgen receptors in each follicle matter more than the systemic level. A dermatologist can usually diagnose androgenetic alopecia by examining the pattern and progression of hair loss. The blood test adds very little to that clinical picture for most patients.

A Better Marker for Peripheral Androgen Activity

Because serum DHT doesn’t capture what’s happening at the tissue level very well, researchers have long searched for blood markers that do. The leading candidate is a metabolite called 3-alpha-androstanediol glucuronide (often abbreviated 3α-diol G). After DHT acts in a target tissue like skin, it gets broken down and tagged with a glucuronide group, which then enters the bloodstream. Since this metabolite originates largely from peripheral tissues rather than the liver, its blood level serves as a rough indicator of how much DHT is actually being produced and used locally.¹¹

Early work established 3α-diol G as the best available marker of DHT formation in target tissues such as skin.¹² In women with excess hair growth, this metabolite has proven particularly useful. A study comparing women with PCOS, idiopathic hirsutism, and healthy controls found that 3α-diol G was elevated specifically in the hirsute groups, regardless of underlying diagnosis.¹³ This makes it more clinically informative than serum DHT alone in evaluating androgen-driven symptoms like unwanted facial or body hair.

That said, 3α-diol G testing is not widely available at standard commercial labs. Your doctor may need to send the sample to a specialty reference lab, and insurance coverage can be inconsistent. It remains more of a research and specialist-level tool than a routine test.

DHT Testing While on Medications

If you’re already taking finasteride or dutasteride, a DHT blood test takes on a different role: it can confirm that the drug is doing its job. Finasteride selectively blocks one form of the 5-alpha-reductase enzyme (type 2), while dutasteride inhibits both type 1 and type 2. Because dutasteride hits both enzyme types, it suppresses serum DHT more aggressively.¹⁴

In men with benign prostatic hyperplasia, dutasteride at a standard dose reduced serum DHT by about 93% at three months. The drug suppressed intraprostatic DHT by a similar margin, about 94% relative to placebo.¹⁵ Research has also measured DHT in hair samples from men taking either drug, confirming that both finasteride and dutasteride significantly lowered DHT concentrations in hair, with dutasteride producing the greater reduction.¹⁶

For topical finasteride applied to the scalp, research has found that both scalp and plasma DHT decrease without significant changes in serum testosterone, suggesting the drug stays relatively localized.¹⁷ If you’re using topical finasteride and your doctor orders a serum DHT test, you may still see some suppression even though you’re applying the drug externally.

Clinically, a post-treatment DHT test can help if symptoms aren’t improving as expected. If serum DHT remains elevated on finasteride, a switch to dutasteride or a dose adjustment could be discussed. But again, the serum-tissue gap means that even with a 90%+ drop in circulating DHT, tissue-level effects are what ultimately determine symptom improvement.

How Testosterone Therapy Affects DHT

Men on testosterone replacement therapy often wonder whether their DHT will spike, and the answer depends on the delivery method. Testosterone gels applied to the skin can push DHT levels up substantially because the skin itself is rich in 5-alpha-reductase. One study noted that testosterone gel can raise plasma DHT by up to 300% above baseline, though injectable testosterone undecanoate also increases DHT by a roughly similar magnitude.¹⁸

A counterintuitive finding emerged from research on elderly men with low testosterone but already-high DHT: when these men received testosterone supplementation, their DHT levels actually declined. On average, DHT dropped from about 0.95 to 0.55 nmol/L, with a pronounced fall in men whose baseline DHT was in the upper range. The researchers attributed this to a downshift in 5-alpha-reductase activity as testosterone supply normalized.¹⁹ The practical takeaway is that the direction of DHT change during testosterone therapy isn’t always predictable from first principles. Your doctor may want to check DHT a few months into therapy to see what actually happened rather than guessing.

Saliva and Alternative Sample Types

Some direct-to-consumer testing companies offer saliva-based hormone panels, and you might see DHT or testosterone included. Saliva testing for endogenous testosterone tracks reasonably well with serum values when an accurate assay is used. However, the picture falls apart for anyone using transdermal testosterone (gels or creams). In people on topical testosterone, saliva testosterone readings are routinely far above the physiological range and don’t correspond to any meaningful clinical parameter.²⁰ Since DHT is produced from testosterone in the skin and salivary glands, similar contamination concerns apply. If you’re using a topical androgen product, saliva-based testing is not a reliable way to monitor your hormone levels.

Urinary steroid profiling is another approach, mainly used in research settings. Twenty-four-hour urine collections can capture the full spectrum of androgen metabolites, including DHT-derived compounds, and have been explored as a way to distinguish hormonal subtypes of PCOS.²¹ This is impractical for routine clinical use, but it hints at a future where a fuller metabolite picture replaces the single-hormone snapshot.

When a DHT Test Is Worth Ordering

Given everything above, the situations where a serum DHT test genuinely changes clinical decisions are narrower than most people expect. The test has its clearest utility in a few settings:

Suspected 5-alpha-reductase deficiency: The testosterone-to-DHT ratio, especially after stimulation testing, helps screen for this rare genetic condition in children and adolescents with ambiguous genital development.⁶ Genetic testing is still needed for confirmation, but the ratio narrows the differential.
Monitoring 5-alpha-reductase inhibitor therapy: If you’re on finasteride or dutasteride for BPH or hair loss and symptoms aren’t improving, a serum DHT test can confirm whether the drug is effectively suppressing the enzyme.
Evaluating hyperandrogenism in women: DHT and the testosterone-to-DHT ratio can add useful information alongside other androgen tests in workups for PCOS or idiopathic hirsutism, especially when combined with 3α-diol G.⁸
Testosterone therapy monitoring: Checking DHT after starting testosterone replacement can help assess the balance of androgen conversion, particularly if prostate-related symptoms emerge.

For the common scenario of a man noticing hair thinning and wanting a blood test to “confirm” that DHT is the culprit, the test is unlikely to change the diagnosis or treatment plan. Androgenetic alopecia is diagnosed clinically, and the treatments (finasteride, minoxidil, dutasteride) are prescribed based on the pattern and progression, not the blood level.

Practical Tips for Getting Tested

If you do get a DHT test, a few practical details can improve the quality of the result. Like testosterone, DHT levels follow a diurnal rhythm, peaking earlier in the day and declining later. Morning blood draws tend to capture the most reproducible values. Fasting isn’t strictly required for a DHT test, but many doctors order it alongside a broader metabolic or hormone panel where fasting does matter, so ask when scheduling.

Make sure the ordering provider specifies the assay method. If the lab uses mass spectrometry, the result will be more accurate, especially at lower concentrations. If only immunoassay is available, the result is still useful for tracking trends over time in the same individual using the same lab, but comparing it to published reference ranges or someone else’s result from a different lab gets unreliable. If you’re comparing a pre-treatment and post-treatment value, use the same lab and same method both times.

Finally, disclose all medications, supplements, and topical products to your doctor before the test. Biotin supplements, which are popular for hair and nail health, can interfere with some immunoassays (not specifically for DHT, but for other hormones often measured on the same panel). Topical testosterone or DHEA creams can affect results in unpredictable ways. And if you’ve recently handled testosterone gel, even washing your hands may not fully remove residue that could contaminate a blood draw site. Let the phlebotomist know so they can choose an appropriate location.

Genetic Conditions Where DHT Testing Has Specific Diagnostic Value

5-alpha-reductase type 2 deficiency is a rare autosomal recessive condition that impairs the conversion of testosterone to DHT. Children born with this condition typically have XY chromosomes but may present with undervirilized or ambiguous genitalia at birth, because DHT is essential for the development of external male genitalia in utero. At puberty, rising testosterone levels can cause partial virilization, and some affected individuals undergo a change in gender role during adolescence.

In a large Chinese cohort of over 100 patients with confirmed 5-alpha-reductase type 2 deficiency, researchers found that the testosterone-to-DHT ratio varied by the specific genetic mutation. Patients homozygous for one common variant (p.R227Q) had a higher ratio than those carrying different mutations, indicating that the severity of enzyme impairment differs across genetic variants.²² This underscores that even within a single diagnosis, no single ratio cutoff works perfectly for everyone, and the blood test is a screening step, not a final answer.

For families with a known history of this condition, genetic counseling and molecular testing remain the gold standard. The DHT blood test, specifically the stimulated testosterone-to-DHT ratio, is most useful as a first-pass screen that tells the clinical team whether genetic testing is warranted, particularly in young children where other diagnostic clues may be ambiguous.