The short version
- A 2024 systematic review covering 52 studies and 27 marketed testosterone-booster ingredients found that most of them fail to increase total testosterone.
- One week restricted to five hours in bed lowered daytime testosterone by 10% to 15% in ten healthy young men, against a normal ageing decline of roughly 1% to 2% a year.
- Weight loss is the clearest lever in the file: pooling 24 studies, a low-calorie diet raised total testosterone by a mean 2.87 nmol/L and bariatric surgery by 8.73 nmol/L.
- Exercise training on its own did not change resting testosterone across 11 randomised trials in 421 insufficiently active men, with a standardised mean difference of exactly 0.00.
- Testosterone deficiency is established with a repeated fasting morning blood test read by a doctor, not inferred from symptoms or from a supplement label.
One week of five-hour nights lowered daytime testosterone in young healthy men by 10% to 15%. Normal ageing lowers it by roughly 1% to 2% a year. Run that arithmetic and a single bad week costs a twenty-five-year-old something in the neighbourhood of what a decade of getting older costs him — and it is usually the same man, at 11pm, reading a supplement label instead of going to bed.
That figure comes from Leproult and Van Cauter's 2011 report in JAMA: ten healthy young men, one week restricted to five hours in bed, testosterone sampled repeatedly across the day. It is a small convenience sample and the authors say so on the page. It is also the number this entire conversation runs on, and nothing since has pointed the other way.
Start with the shelf, because that is where the money goes
In 2024, Morgado and colleagues published a systematic review in the International Journal of Impotence Research covering two decades of testosterone-booster research: 52 studies, 27 different marketed ingredients, four separate populations. Their finding, in their own words, is that most fail to increase total testosterone.
Not "results were mixed." Not "more research is needed." Most of them do not do the single thing the label exists to promise. The exceptions they identified were narrow and population-specific: β-hydroxy β-methylbutyrate and betaine in male athletes; Eurycoma longifolia, a pomegranate-rind and cacao blend, and a purified shilajit extract rated possibly effective in men with late-onset hypogonadism; Eurycoma longifolia and Withania somnifera — ashwagandha — rated possibly effective in healthy men. Zinc and magnesium, five studies between them, did not make that list.
We sell magnesium. We sell ashwagandha. We would rather you read that paragraph than a headline we wrote about either of them.
The levers that do show up
Body fat is the big one. Corona and colleagues pooled 24 studies in European Journal of Endocrinology in 2013. Both a low-calorie diet and bariatric surgery were associated with significant increases in total testosterone — a mean rise of 2.87 nmol/L with diet and 8.73 nmol/L with surgery, both p<0.0001 against baseline. The single best determinant of how much testosterone rose was how much weight came off. This is the clearest dose-response in the whole file, and there is nothing to buy.
Sleep, per the number at the top. Also nothing to buy, strictly speaking, though we will come back to that honestly in a moment.
Training — with an asterisk we are obliged to give you. Potter and colleagues meta-analysed 11 randomised controlled trials covering 421 insufficiently active, apparently healthy men, across aerobic, resistance and combined programs running a median of 12 weeks. The overall effect on resting total testosterone was negligible: a standardised mean difference of 0.00, 95% CI −0.20 to 0.20, unchanged by training mode, age, body mass status or how testosterone was measured. Their conclusion is that exercise training does not appear to affect resting total or free testosterone in men whose levels are already normal.
Read that carefully, because it is easy to over-correct. Training changes body composition, which is the lever that does move the number. It also improves nearly everything you came here for in the first place. What it does not reliably do, on its own, in a man with normal labs, is raise the resting figure on the page.
And the post-workout spike everyone chases? Morton and colleagues put 49 resistance-trained men through 12 weeks of whole-body training with biopsies, strength testing and DXA scans, measuring the acute hormonal response throughout. They found no significant correlations between the acute post-exercise rise in any purported anabolic hormone and the change in strength or hypertrophy. The surge after a hard leg session is real. It does not predict what you build.
Alcohol, honestly
You will see alcohol on every list of testosterone killers, including lists we have written. We went looking for a citation clean enough to put our name on and could not find one. The observational meta-analytic data at low and moderate intake is inconsistent, and the clearest signal sits at the level of alcohol use disorder rather than a Friday night. Drink less if you want to — there are better arguments for it than this one, and we are not going to manufacture a number to make the paragraph land harder.
So where does that leave a supplement company?
Uncomfortable, which is the correct place to be. Here is the version we can defend.
Sleep is the highest-leverage item on this list and the only one you can act on tonight. Magnesium glycinate is not a testosterone product and we are not going to sell it as one — the booster review did not find magnesium raised testosterone, and we are not going to argue with a systematic review because it is inconvenient. What the sleep literature supports is a modest reduction in how long it takes to fall asleep. If short sleep is your actual problem, that is a real lever, and the connection to testosterone is indirect. We would rather write "indirect" than let you assume otherwise.
Ashwagandha is one of the few ingredients that review declined to dismiss for healthy men. That is a low bar and we are calling it a low bar. The stronger case for ashwagandha in men is about cortisol and training stress, which is a different article and a different claim.
What we'd actually tell you
If you are genuinely worried about your testosterone, the first purchase is not a supplement. It is a fasting morning blood test, repeated, ordered by a doctor who will read the number against your symptoms, your medications and your history. Confirmed low testosterone with symptoms is a medical situation with medical management, and nothing on any shelf — ours included — substitutes for that conversation.
If the labs come back normal and you still feel flat: sleep seven hours or more, get your body composition somewhere you are happy with, keep lifting because it is worth doing on its own merits, and stop paying for the aisle. That advice costs us money. It is still the advice.
Good questions
Do testosterone boosters actually work?
Mostly no. A 2024 systematic review of 52 studies across 27 marketed ingredients concluded that most fail to increase total testosterone at all. A few were rated possibly effective in specific groups, and the review did not support zinc or magnesium across the five studies covering them. We sell some of these ingredients, and that is still the honest summary of the shelf.
What actually raises testosterone naturally?
Body fat and sleep are the two levers with the clearest data. Pooling 24 studies, weight loss raised total testosterone by a mean 2.87 nmol/L on a low-calorie diet and 8.73 nmol/L after bariatric surgery, and how much came off predicted how much testosterone rose. Separately, a week of five-hour nights dropped daytime testosterone 10% to 15%. Neither costs anything.
Does lifting weights increase testosterone?
Not the resting number, at least in men whose levels are already normal. A meta-analysis of 11 trials in 421 insufficiently active men found a standardised mean difference of 0.00 on resting total testosterone, unchanged by training mode or age. Lift anyway. Training changes body composition, which is the lever that does move the number, and the acute post-workout hormone spike does not predict what you build.
Are there any testosterone-booster ingredients the research did back?
A handful, narrowly. The 2024 review rated HMB and betaine as effective in male athletes, and Eurycoma longifolia plus ashwagandha as possibly effective in healthy men. Possibly effective is a low bar and we are calling it a low bar. If you want a reason to take ashwagandha, the cortisol and training-stress evidence is stronger than the testosterone evidence.
Should I take zinc or magnesium to boost testosterone?
Not for that reason. The 2024 booster review covered five studies between zinc and magnesium and neither made its list of ingredients that raised total testosterone. We sell magnesium glycinate and we are not going to argue with a systematic review because it is inconvenient. What magnesium has support for is falling asleep faster, and the link from sleep to testosterone is real but indirect.
How do I know if my testosterone is genuinely low?
A blood test, not a symptom checklist. The measurement that counts is a fasting morning total testosterone, repeated on a second morning, ordered by a doctor who will read it against your symptoms, medications and history. Confirmed low testosterone with symptoms is a medical situation with medical management. Nothing on our shelf, or anyone else's, substitutes for that conversation.
Sources
- Morgado A, Tsampoukas G, Sokolakis I, et al. Do “testosterone boosters” really increase serum total testosterone? A systematic review. Int J Impot Res, 2024. View study
- Leproult R, Van Cauter E. Effect of 1 week of sleep restriction on testosterone levels in young healthy men. JAMA, 2011. View study
- Corona G, Rastrelli G, Monami M, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. Eur J Endocrinol, 2013. View study
- Potter NJ, Tomkinson GR, Dufner TJ, et al. Effects of Exercise Training on Resting Testosterone Concentrations in Insufficiently Active Men: A Systematic Review and Meta-Analysis. J Strength Cond Res, 2021. View study
- Morton RW, Oikawa SY, Wavell CG, et al. Neither load nor systemic hormones determine resistance training-mediated hypertrophy or strength gains in resistance-trained young men. J Appl Physiol, 2016. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
