Night Shifts and Testosterone: What Shift Work Does to Your Hormones

He has worked nights at the distribution centre for six years: four on, four off, home at 7am, asleep by 9 if the neighbours are quiet. On his days off he flips back to normal hours to see his kids.

He is 38. He is tired all the time, his gut has thickened, and his interest in sex has quietly gone. His GP tested his testosterone at 11am, after he had come off a night shift and not slept. It came back low. A repeat a month later, on a day off, was normal.

Both results were accurate. That is the problem with shift work and testosterone, and it is why men who work nights need to understand how the two interact.

Testosterone runs on a clock

Testosterone is not released at a steady rate. It is made mostly during sleep, rises through the night and peaks around the time you would normally wake. It then falls through the day. In younger men, the difference between the morning peak and the evening low can be substantial.

That rhythm is driven by two things working together: your internal body clock and sleep itself. Shift work disrupts both. You sleep at the wrong time of day, often for less time, and the clock never fully adjusts, especially if you flip back to daytime hours on your days off.

What losing sleep does

The clearest experiment comes from Leproult and Van Cauter in 2011. Ten healthy young men, average age 24, spent three nights sleeping up to 10 hours, then eight nights restricted to under five hours. After a week of short sleep, their daytime testosterone fell by 10 to 15 per cent, about the drop expected from 10 to 15 years of ageing. Their mood and vigour fell with it.

Shift workers do not always sleep that little, but many come close, and they combine short sleep with sleep at the wrong time.

We cover the general link in does sleep affect testosterone. This article is about what is different when your job moves your sleep around.

What the studies in shift workers show

The most detailed work comes from a group at Baylor College of Medicine. Balasubramanian and colleagues studied 2,571 men attending an andrology clinic. Of the 619 who worked nonstandard shifts, 196 met the criteria for shift work sleep disorder, meaning they had persistent insomnia or excessive sleepiness linked to their work schedule.

After adjusting for age, other illnesses and previous testosterone treatment, shift work sleep disorder was linked to testosterone about 100 ng/dL lower, roughly 3.5 nmol/L, and to noticeably worse symptoms on a standard questionnaire for low testosterone.

The important detail is who was affected. It was not shift work on its own that mattered most, but shift work combined with poor sleep. Men who worked nights but slept reasonably well looked much better than those who did not.

That is encouraging, because sleep is the part you can work on.

Sperm and erections

Related work from the same group, presented in 2017, found lower sperm density and total motile count in infertile men who worked shifts than in those who did not, and a 2020 study of 754 men by Rodriguez and colleagues found that those with shift work sleep disorder had poorer erectile function, with night workers faring worst. These were studies of men already attending clinics, so they show associations rather than proof. They point in the same direction.

The testing trap

This is where shift workers are most often misdiagnosed.

Guidelines say testosterone should be measured in the morning, because that is when it peaks and when reference ranges were set. But "morning" really means a few hours after you wake from your main sleep. For a man who has just finished a night shift and has not slept, a 9am blood test catches him at the low point of his cycle, not the peak.

The result can be a falsely low reading, an unnecessary prescription, or, just as often, a true deficiency missed because the next test happened to fall at a better time.

If you work shifts, tell whoever orders the test. Ask for it to be timed a few hours after you wake from your main sleep, on a typical day of your pattern, and repeated before anyone makes a decision. Our guides to the testosterone blood test and morning versus evening testosterone explain why timing matters so much.

The other things shift work changes

Testosterone rarely moves alone. Shift work is linked to weight gain, insulin resistance and higher rates of type 2 diabetes, partly because eating at night handles sugar less well and partly because tired people eat more and move less. Belly fat in turn lowers testosterone, as we explain in stubborn belly fat in men, and the link with diabetes is covered in testosterone and type 2 diabetes.

Night work also changes cortisol, caffeine intake and alcohol use. Many men use alcohol to get to sleep after a shift, which shortens the deep sleep they most need. See the truth about alcohol and testosterone.

What actually helps

You may not be able to change your rota. You can change how you sleep around it.

Protect the main sleep

• Make the bedroom properly dark. Blackout blinds or a good eye mask. Daylight leaking in is one of the main reasons day sleep is shallow.
• Block noise. Earplugs or a fan. Tell the household when you sleep.
• Aim for a consistent sleep window on work days, even if it is 8am to 3pm. Consistency matters as much as length.
• Add a short sleep before the first night shift of a run, rather than going in having been awake since morning.

Manage light

Light is the strongest signal your body clock receives. Bright light during the shift helps you stay alert; wearing sunglasses on the way home in the morning helps you fall asleep when you get there. Avoid bright screens in bed.

Be careful with caffeine and alcohol

Use caffeine early in the shift rather than in the last few hours, or it will still be working when you try to sleep. Avoid using alcohol as a sleeping aid.

Eat with the shift, not against it

Have your main meal before the shift, and keep night-time eating light: protein, vegetables and some slow carbohydrate rather than vending machine food. Large meals in the small hours are the ones the body handles worst.

Rule out sleep apnoea

If you snore, wake unrefreshed however long you sleep, or your partner notices pauses in your breathing, get checked. Sleep apnoea is common in men who carry weight around the middle and it independently lowers testosterone, as we explain in sleep apnoea and testosterone.

When to see someone

If you have symptoms of low testosterone, persistent insomnia or excessive sleepiness that you link to your shifts, both deserve attention. Shift work sleep disorder is a recognised condition, and treating the sleep may do more for your hormones than treating the hormones directly.

If repeat, well-timed tests still show low testosterone, the usual investigation applies, starting with the causes in what causes low testosterone.

Common questions

Does working nights lower testosterone?

It can, mainly through shorter and poorly timed sleep. In a study of over 2,500 men, those with shift work sleep disorder had lower testosterone and worse symptoms than other men, even after adjusting for age and health.

Is it the shift work or the poor sleep?

Mostly the poor sleep. Shift workers who slept well looked much better than those with shift work sleep disorder, which is why improving day sleep is the main lever.

When should a shift worker have a testosterone test?

A few hours after waking from your main sleep, on a typical day of your pattern, rather than straight after a night shift. Tell whoever orders it about your hours, and repeat any low result.

Will a week of short sleep really lower testosterone?

In one well-known study, young men sleeping under five hours a night for a week saw daytime testosterone fall by 10 to 15 per cent.

Do sleeping tablets or melatonin help?

They can help some people in the short term, but they should be discussed with a doctor. Light, darkness, noise and timing are the foundation and have no side effects.

Sources: Leproult R, Van Cauter E, Effect of 1 week of sleep restriction on testosterone levels in young healthy men, JAMA 2011;305(21):2173-4 · Balasubramanian A et al., Increased risk of hypogonadal symptoms in shift workers with shift work sleep disorder, Urology 2020;138:52-9 · American Urological Association Annual Meeting 2017, abstracts on shift work, semen parameters and lower urinary tract symptoms · Rodriguez et al., Shift work sleep disorder and night shift work significantly impair erectile function, J Sex Med 2020;17:1687-93 · Educational only, not medical advice.

Keep reading: Does sleep affect testosterone? · Sleep apnoea and testosterone · The 90-minute sleep rule · Why you wake up tired after 8 hours · Blood test: what to check · Testosterone and type 2 diabetes