Low Libido in Men Over 40: Causes and What to Test in NZ

In short: a lower sex drive after 40 is common and usually has more than one cause. Stress, poor sleep, relationship strain, depression, some antidepressants, alcohol and excess weight are the usual suspects. Low testosterone is one possible cause, and it's more likely when low desire comes with fewer morning erections. Two morning blood tests, with prolactin and thyroid checked, will tell you whether hormones are part of it.

Desire changes over a lifetime, and a dip after 40 doesn't automatically mean something is wrong. It's worth looking into when the change is clear, has lasted a few months, and bothers you or your partner. This guide covers the common causes, how to tell a hormone problem from everything else, and the tests that settle it.

Is a lower sex drive after 40 normal?

Some drift is normal. Long relationships, kids, work and fatigue all take a toll on desire, and none of that is a medical problem. What's less normal is a clear change from your own baseline: you used to want sex and now you rarely think about it, or the change came on over months without an obvious reason.

That second pattern is worth checking, because several of its causes are treatable, and one of them, low testosterone, has a specific test.

Common causes of low libido in men over 40

Most men with low desire have more than one thing going on:

• Stress and fatigue. Long hours, money worries and young children compete directly with desire.
• Relationship factors. Conflict, resentment or a mismatch in what each person wants are common and often unspoken.
• Depression and anxiety. Loss of interest in things you used to enjoy, sex included, is a core feature of depression.
• Medicines. Some antidepressants commonly reduce desire or delay orgasm. In a meta-analysis, the antidepressants that caused more sexual side effects than placebo did so in about a quarter to four-fifths of people (26% to 80%, depending on the medicine), while several others showed no significant difference from placebo (Serretti and Chiesa, 2009). Opioids, some antipsychotics, high-dose corticosteroids and 5-alpha reductase inhibitors (such as finasteride) are also linked with low testosterone or its symptoms (BPAC NZ 2024). Healthify's guide to medicines and sexual problems lists antidepressants (especially SSRIs), antipsychotics, some blood pressure medicines and opioids among the medicines known to cause sexual problems, and advises against stopping a medicine abruptly (Healthify). Talk to the prescriber about options instead.
• Alcohol. Chronic heavy drinking is linked with low testosterone (BPAC NZ 2024) and dulls sexual response.
• Poor sleep and sleep apnoea. Sleep deprivation lowers testosterone, and obstructive sleep apnoea is linked with lower testosterone; in a meta-analysis the difference was clear only in severe apnoea (Su et al., 2022).
• Excess weight and diabetes. Body fat lowers testosterone, and losing weight raises it (Corona et al., 2013).
• Erection problems. Men who've had a few failed erections often start avoiding sex, and that avoidance can feel like low desire.
• Low testosterone. Real, but only one item on the list. Healthify lists low libido and erectile dysfunction as its most common symptoms (Healthify).
• High prolactin or thyroid problems. Less common, but both can lower desire and both show up on a blood test. High prolactin can cause low libido and erectile dysfunction in men (Melmed et al., 2011), and in a small study 64% of men with an underactive thyroid had low desire (Carani et al., 2005).

Is it low testosterone? The signs that point to hormones

It can be. In the European Male Ageing Study of 3,369 men aged 40 to 79, low sexual desire was one of three sexual symptoms that clustered with low testosterone. The other two were fewer morning erections and erectile dysfunction (Wu et al., 2010). BPAC lists the same three as the symptoms most indicative of low testosterone (BPAC NZ 2024).

So the pattern matters more than any single symptom:

Low libido or erectile dysfunction? Why the difference matters

These get mixed up, and the difference changes what helps. Low libido is about wanting sex. Erectile dysfunction is about the mechanics: getting or keeping an erection when you do want it.

Erection tablets help with the mechanics. They don't create desire. A man with low desire who's prescribed one often finds it does little, because the problem was never blood flow. On the other hand, a man whose erections have become unreliable can lose interest in sex to avoid the stress of it, and fixing the erection problem often brings desire back. If you're not sure which came first, our guide on ED in your 40s and 50s covers the erection side. Healthify also notes that erection problems can be an early sign of diabetes or heart disease, which is another reason to get them checked (Healthify).

Low libido blood tests: what to ask for in NZ

A sensible work-up for low desire that has lasted a few months:

• Total testosterone, twice, in the morning. BPAC advises 7 to 11 am, ideally fasting, with a low result repeated about four weeks later (BPAC NZ 2024). For shift workers, BPAC advises two to three hours after waking.
• SHBG, so free testosterone can be calculated. This matters in older men, whose SHBG tends to rise.
• LH and FSH, to show whether a low result starts in the testes or the pituitary.
• Prolactin, especially if testosterone is low and LH isn't raised.
• TSH for thyroid function.
• HbA1c and lipids, because diabetes and blood vessel disease affect both desire and erections.
• A mood screen. A few questions about mood and interest are as important as the bloods.

Enhanced Men diagnoses low testosterone when a man has symptoms and two morning results, three to four weeks apart, both below 12 nmol/L total testosterone (the European Association of Urology threshold) or 225 pmol/L free testosterone. Above that line is not low testosterone.

A note on units. New Zealand labs report testosterone in nmol/L, while American sources use ng/dL. To convert nmol/L to ng/dL, multiply by 28.84; to go the other way, divide by 28.84. The 300 ng/dL cut-off used in American urology guidance (Mulhall et al., 2018) is about 10.4 nmol/L, and 12 nmol/L is about 346 ng/dL. Our normal testosterone levels guide has a full conversion table.

Does testosterone treatment help libido?

Only when testosterone is confirmed low, and then modestly. In the Testosterone Trials, men aged 65 and over with low testosterone and symptoms reported more sexual activity, desire and erectile function on testosterone gel than on placebo over a year, but the effect was moderate, not dramatic (Snyder et al., 2016). Those were older men, so results in younger men, or with other causes of low testosterone, may differ.

If testosterone is normal, taking more won't fix desire and brings its own risks, including suppressed sperm production and a rise in red blood cells (Bhasin et al., 2018). Healthify notes that men whose levels sit in the bottom of the normal range aren't usually treated with testosterone (Healthify). The better targets are the causes above: sleep, alcohol, weight, mood, medicines and the relationship itself. Couples or sex therapy is a legitimate medical treatment for low desire, not a soft option.

How do you get your libido back in your 40s?

Work on the causes you can change, roughly in this order:

• Sleep. Protect it, and get loud snoring or daytime sleepiness checked for sleep apnoea.
• Alcohol. Cut back for a month and see what changes.
• Weight and exercise. Losing excess weight raises testosterone in men carrying extra weight, and regular exercise helps mood and erections.
• Medicines. Ask your prescriber whether anything you take can affect desire, and whether there's an alternative.
• Mood and stress. Treating depression or anxiety can bring desire back; if a medicine is part of the treatment, ask about options with fewer sexual side effects.
• The relationship. Talk about it. Couples or sex therapy is a legitimate treatment for low desire.
• Bloods. If low desire comes with fewer morning erections, test testosterone properly, along with prolactin and thyroid.

What to do next

1. Notice the pattern. Is it desire, erections, or both? Did it start with a new medicine, a new job or a hard year?
2. Take the free AMS self-check. Anonymous, 17 questions, with a score that tells you whether a blood test is worth doing.
3. Get the bloods done properly. Your GP can request the panel above, or see where to get it checked, below.
4. If you're feeling low as well, tell your doctor. In New Zealand you can also call or text 1737, free, any time, to talk with a trained counsellor or peer support worker.

Where to get low libido checked in NZ

Low libido needs testosterone, prolactin and thyroid checked, and a conversation about mood, medicines and your relationship. The two usual routes are below, and neither needs a referral.

Your GP. Your GP can request the same morning tests, repeat them and start treatment when low testosterone is clearly there. If two morning results fall between 8 and 12 nmol/L, BPAC suggests your GP consider discussing them with an endocrinologist.

A private doctor by video. Enhanced Men, which publishes this guide, is a New Zealand telehealth clinic run by Dr Jack Yeoman, who does every consult himself. He's registered with the Medical Council of New Zealand in general scope (MCNZ 89436). General scope isn't a specialist registration, and it isn't general practice either: he isn't vocationally registered as an endocrinologist, a urologist or a GP, and he refers you on when your case needs a specialist. You see him by video wherever you live in New Zealand, with no GP referral. Your bloods are taken at your local community lab; if you're eligible for publicly funded healthcare, funded tests cost you nothing, and the lab bills you for any test that isn't funded. He diagnoses low testosterone only when you have symptoms and two morning results, three to four weeks apart, both below 12 nmol/L total or 225 pmol/L free testosterone. Above that line is not low testosterone, and he doesn't prescribe for it. Testosterone treatment usually suppresses sperm production. If you may want children, say so before you start.

Whichever route you choose, take copies of any earlier results, with the time each sample was taken, and what your GP made of them.

FAQ

Is it normal for a man over 40 to lose interest in sex? Some drop in desire with age, stress and long relationships is common. A clear change from your usual baseline that lasts a few months is worth checking, because causes such as depression, medicines, sleep apnoea and low testosterone are treatable.

Is low libido a sign of low testosterone? It can be. Low sexual desire is one of the three symptoms most specifically linked to low testosterone, along with fewer morning erections and erectile dysfunction. Low desire on its own, with normal erections, is more often caused by stress, fatigue, mood or relationship factors.

What blood tests check for low libido in men? Two morning total testosterone tests about four weeks apart, SHBG to calculate free testosterone, LH and FSH, prolactin, thyroid function (TSH), and HbA1c and lipids. A short mood screen belongs alongside the bloods.

Can antidepressants lower libido? Yes. Several commonly used antidepressants cause sexual side effects, including lower desire, in a large share of people who take them, while others caused no more sexual side effects than placebo in studies. If you think a medicine is affecting your sex drive, talk to your prescriber rather than stopping it yourself.

Why is my husband's libido so low? Usually for several reasons at once: stress, tiredness, poor sleep, low mood, alcohol, a medicine side effect, unspoken relationship strain, or worry about erections. Low testosterone is one possible cause. If it has lasted a few months, a GP visit with morning blood tests is a sensible step, and talking about it together helps more than guessing.

Do erection tablets help low libido? Not directly. They help with getting and keeping an erection, not with wanting sex. They can help indirectly when low desire is really avoidance after erection problems.

Where can I get my libido and hormones checked in NZ? Your GP can check testosterone, prolactin and thyroid and look at mood and medicines. You can also see a private doctor: Enhanced Men, Dr Jack Yeoman's telehealth clinic, assesses low libido by video anywhere in New Zealand with no referral and gives you a lab request form for your local community lab. Low testosterone is diagnosed only when you have symptoms and two morning results, three to four weeks apart, both below 12 nmol/L total or 225 pmol/L free.

References

1. Wu FCW, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. N Engl J Med. 2010;363(2):123–35. https://doi.org/10.1056/NEJMoa0911101
2. BPAC NZ. Prescribing testosterone in ageing males. 25 November 2024. https://bpac.org.nz/2024/testosterone.aspx
3. Serretti A, Chiesa A. Treatment-emergent sexual dysfunction related to antidepressants: a meta-analysis. J Clin Psychopharmacol. 2009;29(3):259–66. https://doi.org/10.1097/JCP.0b013e3181a5233f
4. Su L, et al. Association between obstructive sleep apnea and male serum testosterone: a systematic review and meta-analysis. Andrology. 2022;10(2):223–31. https://doi.org/10.1111/andr.13111
5. Corona G, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. Eur J Endocrinol. 2013;168(6):829–43. https://doi.org/10.1530/EJE-12-0955
6. Melmed S, et al. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(2):273–88. https://doi.org/10.1210/jc.2010-1692
7. Snyder PJ, et al. Effects of testosterone treatment in older men. N Engl J Med. 2016;374(7):611–24. https://doi.org/10.1056/NEJMoa1506119
8. Bhasin S, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–44. https://doi.org/10.1210/jc.2018-00229
9. Mulhall JP, et al. Evaluation and management of testosterone deficiency: AUA guideline. J Urol. 2018;200(2):423–32. https://doi.org/10.1016/j.juro.2018.03.115
10. Carani C, et al. Multicenter study on the prevalence of sexual symptoms in male hypo- and hyperthyroid patients. J Clin Endocrinol Metab. 2005;90(12):6472–9. https://doi.org/10.1210/jc.2005-1135
11. European Association of Urology. EAU Guidelines on Sexual and Reproductive Health, 2026 edition: Male hypogonadism (section 3.3.5). https://uroweb.org/guidelines/sexual-and-reproductive-health/chapter/male-hypogonadism
12. Healthify NZ. Medicines and sexual problems. Reviewed 10 February 2025. https://healthify.nz/medicines-a-z/m/medicines-and-sexual-problems
13. Healthify NZ. Testosterone deficiency. Reviewed 13 December 2024. https://healthify.nz/health-a-z/t/testosterone-deficiency
14. Healthify NZ. Erectile dysfunction. Reviewed 5 November 2025. https://healthify.nz/health-a-z/e/erectile-dysfunction
15. Healthify NZ. Testosterone replacement therapy. Reviewed 5 April 2024. https://healthify.nz/medicines-a-z/t/testosterone-replacement-therapy
16. 1737, Need to talk? Free 24/7 call or text support, run by Whakarongorau Aotearoa | New Zealand Telehealth Services. https://1737.org.nz/

This article is general health information, not personalised medical advice. If your sex drive has changed, a doctor can help work out why; the cause is often something other than hormones.