PFS blood tests: what to consider and why

Thinking about blood tests for post-finasteride syndrome (PFS), a condition that can last after stopping finasteride? No blood test diagnoses it. Tests look for other causes of your symptoms, and a normal result doesn’t rule PFS out.

The UK Propecia leaflet lists erection, sex drive and ejaculation problems that persisted “after discontinuation of treatment”. No blood test measures that.

Chirag took his last finasteride tablet on 1 January 2024. By the time he spoke to Moral Medicine he had seen five or six doctors. “My test levels are normal,” he says.

If you’ve been told the same, his interview shows what that can feel like.

Play video: Doctors Said Post-Finasteride Syndrome Wasn’t Real. Then It Happened to Him

So which tests are worth asking for, and what if yours come back normal?

Which blood tests help, and why?

Because they can find something else that needs treating. The PFS criteria ask that no other medical condition could explain the symptoms, and blood tests help check that part.

They can’t do the rest. The criteria also look at your medicine history and what changed after you stopped. A blood test can’t show whether finasteride caused your symptoms.

There’s no standard “PFS blood panel”. What gets tested depends on your symptoms, your history and what your GP is looking for. Before the appointment, it helps to know what each test is for.

These are the tests that come up most in our community. They’re examples to talk through with your GP, not a checklist for everyone.

• Sex hormones (testosterone, DHT, oestradiol, LH, FSH, SHBG): check whether hormone levels are in the usual range.
• Thyroid tests (TSH, free T4, sometimes free T3): look for a thyroid problem, which can cause tiredness, low mood and low sex drive.
• Cortisol: checks the stress hormone made by the adrenal glands. Timing matters, so ask when the sample should be taken.
• A metabolic panel: checks blood sugar, kidney and liver function and salts in the blood.
• Vitamins and minerals (vitamin D, B12, others): look for low levels that can add to tiredness or low mood.

None of these can show whether you have PFS.

My blood tests are normal. What does that mean?

“Normal” means a result falls within the laboratory’s reference range. It doesn’t mean your symptoms aren’t real, or that every cause has been checked.

PFS is more than sexual problems. The 2022 diagnostic criteria say problems with cognition, depression and suicidality can come with it, and can occur without any sexual difficulties.

For PFS, normal hormones are common. A Harvard study compared men with lasting symptoms after finasteride with men who’d taken it without problems, and men who never had. Testosterone, DHT, oestradiol, LH, FSH and SHBG “did not differ significantly among groups”. The study was small.

Our article on whether finasteride lowers testosterone goes into the hormone side in more detail. Researchers in Milan have also looked for changes in hormones in the fluid around the brain, which a blood test can’t reach.

A normal result doesn’t measure numbness, low mood or problems with cognition. Describe those even if nobody asks.

What if a result is abnormal?

A high, low or borderline result needs an explanation from your GP. It doesn’t confirm PFS, and it shouldn’t be brushed aside because you suspect PFS.

The authors of the PFS criteria write that borderline hormone levels “may be a consequence of the conditions rather than a cause”. Low testosterone has other causes too, so it still needs looking into.

Ask for the actual number and its reference range, not just “normal” or “abnormal”. Keep a copy with the date.

One test needs a warning. The UK leaflet says finasteride “can affect the result” of PSA, a blood test for prostate cancer. If you’re having a PSA test, tell the person testing you that you take or took finasteride.

Dr Michael Irwig, a hormone specialist, published one of the first studies of PFS in 2011. This short film is background on why hormone tests may miss what’s going on. It isn’t advice about your results.

Play video: Persistent sexual side effects of finasteride (Propecia) for male pattern hair loss

How can I prepare for my GP appointment?

Finasteride helps many men keep their hair. If you have side effects, that’s a decision for you and your prescriber. The UK leaflet says to stop taking it and contact your doctor if you have depression.

Bring a short record:

• The medicine: “Finasteride 1 mg from May 2022, last tablet February 2024.”
• The changes: genital numbness, low sex drive, erection problems, and changes beyond sex, such as low mood or problems with concentration and memory. Note when each began.
• Earlier tests: copies with dates and reference ranges, plus other medicines and supplements.

Many people say it took time to be taken seriously. Bring the leaflet line. You can report it without a doctor agreeing. Before the appointment, others in our WhatsApp peer support groups can tell you how they raised it.

Report it: it helps everyone

A doctor’s note helps you. A report to the medicines regulator helps everyone else: it is how patterns get noticed.

• No proof needed. A suspicion is enough, even years after stopping. Normal blood tests don’t stop you reporting.
• Where: the Yellow Card scheme in the UK, MedWatch in the US. Our guides cover Yellow Card and the FDA step by step.
• Use the right words. If symptoms continued after stopping, write Post 5-alpha-reductase inhibitor syndrome (MedDRA 10082430).

Our reporting guide walks you through it

What else do people ask?

Can a private hormone test diagnose PFS? No. A private test measures hormone levels, not PFS. Before paying for a panel, ask what each test looks for and who will explain the results. Take any results to your GP so they sit in one record.

Is a saliva cortisol test better than a blood test? They measure cortisol in different ways, and neither can show PFS. Cortisol changes through the day, so the timing of the sample matters more than people expect. Your GP can say which fits your symptoms.

Chirag’s tests came back normal, and his symptoms were still there. If symptoms of PFS have lasted since your last tablet, report them, whatever your blood tests say.

Sources

1. Healy D, Bahrick A, Bak M and colleagues. Diagnostic criteria for enduring sexual dysfunction after treatment with antidepressants, finasteride and isotretinoin. Int J Risk Saf Med 2022;33(1):65-76. Proposed criteria from expert agreement, not a blood-test study. Section 5 (PFS): cognitive impairment, depression and suicidality “can occur independently of any sexual difficulties”. Each condition requires no current medical condition that could account for the symptoms. Borderline hormone levels “may be a consequence of the conditions rather than a cause”. Full text not re-opened on 22 October 2026 (captcha); wording as verified for other SIDEfxHUB articles.
2. Organon. Propecia 1 mg patient information leaflet, electronic Medicines Compendium. “Frequency unknown”: “persistent difficulty having an erection after discontinuation of treatment”, “persistent decrease in sex drive after discontinuation of treatment”, “persistent problems with ejaculation after discontinuation of treatment”. Stop and talk to your doctor if you experience depression. PSA: “Propecia can affect the result of this test.”
3. Basaria S, Jasuja R, Huang G and colleagues. Characteristics of men who report persistent sexual symptoms after finasteride use for hair loss. J Clin Endocrinol Metab 2016;101(12):4669-80. 56 men (25 with persistent symptoms, 13 finasteride users without, 18 non-users). Serum total and free testosterone, DHT, LH, FSH, oestradiol and SHBG “did not differ significantly among groups”; levels within the normal range. Cross-sectional; thyroid and cortisol not measured.
4. Melcangi RC and colleagues. Neuroactive steroid levels and psychiatric and andrological features in post-finasteride patients. J Steroid Biochem Mol Biol 2017;171:229-35. 16 men; changes in cerebrospinal fluid did not exactly reflect those in plasma.
5. NHS. Blood tests.
6. GOV.UK. Report a problem with a medicine or medical device.
7. Moral Medicine, Doctors Said Post-Finasteride Syndrome Wasn’t Real. Then It Happened to Him, March 2025.
8. PFS Foundation, Persistent sexual side effects of finasteride (Propecia) for male pattern hair loss, August 2012. Used for background, not as evidence about blood tests.

The list of tests reflects what our community discusses. It isn’t clinical guidance. Sources checked on 22 October 2026. AI-assisted writing and review, not clinical review.