Quick answer

In trials, most changes took weeks. Self-rated mood shifted in the first week of one trial, and menopause rating scores were checked after 6 weeks to 4 months. Most trials stopped at 12 weeks, so nobody has studied what longer use does.^1,2

Key facts

In healthy men, desire on maca was no different from placebo at week 4 and higher from week 8.^3,4
A two-week trial in 8 cyclists found no significant difference in desire.⁴
One trial checked sperm at 6 and 12 weeks.⁵
The longest controlled trials ran for about 4 months.⁶

What changed, and when

When trials first saw a difference from placebo^1,3,6,7
Outcome	First difference from placebo	Trial length
Self-rated mood, adults at low altitude	Week 1	12 weeks
Self-rated energy, adults at low altitude	Week 2	12 weeks
Self-rated desire, healthy men	Week 8, not week 4	12 weeks
Self-rated desire, adults in Peru	Week 12, red maca at high altitude only	12 weeks
Menopause rating scores	By the end of each trial	6 weeks to 4 months

In healthy men, self-rated desire on maca was no different from placebo at week 4 and was higher from week 8.^3,4

In the 2016 trial, at low altitude, self-rated mood on maca differed from placebo from the first week and energy from the second week.¹

Why the answer is in weeks, not hours

Trials asked people to take maca every day and checked them at weekly or monthly visits. That design says nothing about what happens in the hours after a single dose, so there is no evidence that maca kicks in on the day you take it.^1,3

Placebo groups also changed. In the 2016 trial, people living at high altitude reported better mood over time even on placebo, which is one reason a quick change in how you feel is hard to credit to maca.¹

Sperm and hormones take longer to measure

Trials of sperm measures ran for 12 weeks or more, and one took samples at 6 and 12 weeks. A pooled analysis of these trials found no clear change in sperm concentration. Testosterone in healthy men was checked at 2, 4, 8 and 12 weeks and did not change at any point.^5,8,9

How long can you keep taking it?

Most trials lasted 6 to 12 weeks and the longest controlled trials about 4 months, so the effects of longer use are unknown.^2,4,6

Most trials in the 2010 review also had no follow-up after people stopped, so nobody knows how long any change lasts once you stop taking maca.⁴

While you wait

Side effects in trials were uncommon and mostly mild, such as stomach upset or headache. No safe upper amount has been set, and no trial showed that a larger amount works faster, so taking more to speed things up is not supported by evidence.^2,4,10

If you are pregnant or breastfeeding, have liver disease or high blood pressure, or take a prescription medicine, ask a doctor or pharmacist before starting.¹¹

Questions people ask

Does maca work right away?

There is no evidence that it does. Trials checked people after days or weeks of daily use, and the earliest change was in self-rated mood after one week in one trial.¹

Do maca pills work faster than powder?

No trial compared them. Capsules, tablets, powder and extracts were all taken daily for weeks before results were measured.⁴

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.