It's a popular theory: men with more testosterone go bald sooner. But does testosterone cause hair loss, or is it more complicated than that? The short answer is that testosterone plays a part, but it's a hormone made from testosterone, called DHT, and how sensitive your hair follicles are to it, that really matter.
This guide explains how testosterone and DHT affect your hair, why genetics play such a big role, and how treatments like finasteride and Regaine work.
Having high testosterone doesn't mean you're destined to go bald. Your genes decide how strongly your hair reacts to it.
What does testosterone do?
Testosterone is the main male sex hormone. It drives the development of male reproductive organs and characteristics like a deeper voice, muscle growth and body hair.
Most testosterone in your blood is bound to proteins, including one called sex hormone binding globulin (SHBG). Only a small amount circulates freely, and it's the free and loosely bound testosterone that your body can actually use.1
This is one reason a single testosterone blood test doesn't tell the whole story when it comes to hair.
What is DHT?
DHT (dihydrotestosterone) is a more powerful hormone made from testosterone. An enzyme called 5-alpha reductase converts some of the testosterone in your body into DHT.2
DHT binds more strongly to androgen receptors than testosterone does. It plays an important role in male development before birth and during puberty, and it helps maintain the prostate in adult men.2
Think of DHT as testosterone's stronger cousin. It's DHT, rather than testosterone itself, that has the biggest effect on scalp hair.
How does DHT cause hair loss?
Your hair grows in cycles: a long growing phase, a short transition and a resting phase, after which the hair falls out and a new one starts.
In men who are genetically prone to male pattern hair loss, DHT gradually shrinks the hair follicles on the scalp. Each new hair grows back thinner and shorter, and the growing phase gets shorter too. Eventually, some follicles stop producing visible hair altogether.3
“Male pattern hair loss involves inherited sensitivity to DHT, a hormone made from testosterone, rather than simply having high testosterone levels. DHT gradually shrinks susceptible hair follicles. Medicines such as finasteride and minoxidil can help, but continued use is needed to maintain their benefit, so speak to a pharmacist or prescriber about what suits you.
Ana Carolina GoncalvesSuperintendent Pharmacist
Why genetics matter more than testosterone levels
The key factor is how sensitive your scalp follicles are to DHT. This sensitivity is largely inherited, which is why male pattern hair loss tends to run in families.3
So a man with average or even low testosterone can still lose his hair early if his follicles are very sensitive to DHT. And a man with high testosterone may keep a full head of hair if they're not.
Look at your family tree rather than your gym results. A history of hair loss in close relatives is a much stronger clue than muscle mass.
How can you treat DHT-related hair loss?
There are licensed treatments that can slow male pattern hair loss and help some hair grow back. They work in different ways.
Finasteride
Finasteride is a prescription tablet taken once a day. It blocks 5-alpha reductase, the enzyme that turns testosterone into DHT, which lowers DHT levels in the scalp.
In clinical trials, hair counts in a small area of the scalp rose by an average of 88 hairs in men taking finasteride 1mg for two years, while men taking a placebo lost an average of 50 hairs.4 It can take 3 to 6 months to notice a difference, and any benefit fades if you stop taking it.3
Finasteride isn't licensed for women.
Finasteride can cause side effects in some men, including low mood, depression, suicidal thoughts and sexual problems such as reduced sex drive and erectile dysfunction. In some cases, sexual side effects have continued after stopping treatment.5 Packs now include a patient card explaining these risks. If you develop low mood, stop taking finasteride and get medical advice, and tell your prescriber about any sexual side effects.5
Mood changes on finasteride are not something to wait out. Speak to a doctor as soon as you notice them.
If you get finasteride through Pharmica, we recommend temporarily stopping it if you or your partner are planning to conceive. Speak to your prescriber before you start taking it again. If your partner is or may be pregnant and you carry on taking finasteride on your prescriber's advice, Pharmica's consultation requires you to use a condom during sex. She must not handle crushed or broken tablets. The amount in semen is small and the risk is considered low, but ask your prescriber how this applies to you.
Minoxidil (Regaine)
Minoxidil is a lotion or foam you apply to your scalp. It's thought to work by improving blood flow to the follicles and extending the hair's growing phase, although the exact mechanism isn't fully understood.
Regaine Extra Strength Solution and Regaine Foam for Men contain minoxidil. Unlike finasteride, minoxidil can also be used by women, with options such as Regaine for Women Solution and Regaine for Women Extra Strength Foam.
Like finasteride, minoxidil only works for as long as you use it, and it doesn't work for everyone.3 Some people notice extra shedding in the first few weeks as old hairs make way for new ones.
Caffeine shampoos
Lab research suggests caffeine may counteract some of the effects of testosterone on hair follicles and extend the growing phase.6 But this research was carried out on hair follicles in a lab rather than in people, so the real-world evidence is limited.
Caffeine products such as Alpecin Shampoo and Alpecin Liquid are cosmetic products rather than licensed medicines. They're best seen as an add-on rather than a replacement for proven treatment.
Finasteride and minoxidil work in different ways, which is why some men use both. A prescriber can tell you whether combining them is right for you.
When should you see a GP?
Pattern hair loss is a normal part of ageing for many men. But speak to a GP if:
- Your hair is falling out suddenly or in patches
- You have bald patches, itching or a rash on your scalp
- You're losing hair and feel unwell in other ways
- Hair loss is affecting your confidence or mood
Hair loss isn't always genetic. Stress, illness and some nutritional deficiencies can also trigger shedding.3 Visit our Health Hub for more on hair loss causes and treatments.
Frequently asked questions
Does finasteride lower testosterone?
No, finasteride doesn’t lower testosterone. It blocks the enzyme that turns testosterone into DHT, so DHT levels fall while testosterone levels usually stay the same or rise slightly. Finasteride can still cause side effects in some men, including sexual problems and low mood, so read the patient card in your pack. If you develop low mood or suicidal thoughts, stop taking finasteride and get medical advice. Tell your prescriber about any sexual side effects.
Does low testosterone cause hair loss?
Low testosterone isn’t a common cause of scalp hair loss. Male pattern baldness depends mainly on how sensitive your follicles are to DHT, which is largely inherited. Low testosterone can cause other symptoms, such as tiredness, low sex drive and reduced body hair. If you’re worried about your hormone levels, a GP can arrange a blood test.
A DHT blocker is anything that reduces the amount of DHT in the body or stops it acting on hair follicles. Finasteride is the main licensed DHT blocker for male pattern hair loss. Many shampoos and supplements are marketed as natural DHT blockers, but the evidence for them is much weaker than for licensed treatments.
Can you use finasteride and minoxidil together?
Yes, many men use both, as they work in different ways. Finasteride lowers DHT, while minoxidil is thought to improve blood flow to the follicles and extend the growing phase. Speak to a prescriber before combining treatments, so they can check both are suitable for you and talk you through possible side effects.
Does testosterone replacement therapy cause hair loss?
It can speed up hair loss in men who are already genetically prone to male pattern baldness. Testosterone therapy can raise DHT levels, which may affect sensitive hair follicles. If you’re starting or already taking testosterone and are worried about your hair, speak to the doctor managing your treatment about your options.
References
- Czub MP, Venkataramany BS, Majorek KA, et al. Testosterone meets albumin: the molecular mechanism of sex hormone transport by serum albumins. Chemical Science. 2019;10(6):1607-1618. doi:10.1039/c8sc04397c
- Society for Endocrinology. Dihydrotestosterone. You and Your Hormones; 2018. yourhormones.info
- NHS. Hair loss. NHS website; 2023. nhs.uk
- Organon Pharma (UK) Limited. Propecia 1 mg Film-Coated Tablets: Summary of Product Characteristics. Electronic Medicines Compendium; 2026. medicines.org.uk/emc
- Medicines and Healthcare products Regulatory Agency. Finasteride: reminder of the risk of psychiatric side effects and of sexual side effects (which may persist after discontinuation of treatment). GOV.UK; 2024. gov.uk
- Fischer TW, Herczeg-Lisztes E, Funk W, et al. Differential effects of caffeine on hair shaft elongation, matrix and outer root sheath keratinocyte proliferation, and transforming growth factor-beta2/insulin-like growth factor-1-mediated regulation of the hair cycle in male and female human hair follicles in vitro. British Journal of Dermatology. 2014. pubmed.ncbi.nlm.nih.gov
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.