Does quercetin boost endurance?

Short answer

Barely. Pooling studies where people took 1,000 mg a day for 1-4 weeks, endurance improved only 0.74-2%, and in people already doing endurance training the effect was 0.09%, no difference.

Does quercetin boost endurance?
'More endurance in mice → more endurance in people' — does this formula hold?
Quercetin is a plant compound found in onions, apples and berries, sold as an endurance supplement. The starting point was mouse studies where it raised the muscles' ability to use oxygen and endurance. We checked whether that carries over to people.
The first small studies looked good
7 days of use: 13.2% longer ride to exhaustion
12 people took 1,000 mg a day for 7 days; their maximum oxygen uptake rose 3.9% and time cycling to exhaustion rose 13.2%. In a 2-week study of 26 people, distance in a 12-minute run rose 2.9%, while it fell 1.2% on placebo.
Repeating it at the same dose
no difference in maximum oxygen uptake or performance
In 30 people taking 1 g a day for 7-16 days, a 10-minute all-out cycling test did not differ from placebo. In 11 people taking it for 5 days, maximum oxygen uptake did not change. In 16 people taking it for 8.5 days, cycling time was 18.3 minutes versus 18.5 on placebo, no difference.
Pooling the studies
an average of 1-2%, which the authors themselves called tiny
An analysis pooling 11 studies and 254 people found about a 2% effect, which the authors rated 'between trivial and small'. Another analysis pooling 288 people found endurance performance improved 0.74% and maximum oxygen uptake 1.94%. It concluded the effect was trivial in practice.
In people who already trained for endurance
the effect was 0.09%, no difference
In that same analysis, the effect showed up only in people who did not exercise regularly (0.83%); in people already doing endurance training it was 0.09%. In a 2024 study, 50 people took 1,000 mg a day for 4 weeks, and 20 km cycling time stayed put, from 30.15 to 30.19 minutes.
One reason is absorption
The 2026 International Society of Sports Nutrition rating: weak evidence
In its 2026 position stand, the International Society of Sports Nutrition rated the evidence for quercetin's exercise effects as weak/low. Most quercetin is broken down in the gut and liver, so little stays in the blood. The same statement named creatine, omega-3 and tart cherry as better-supported options.
Bottom line: little reason to take it for endurance
What worked in mice barely carried over to people
Taking 1,000 mg a day for 1-4 weeks gave an average effect of 0.74-2%, and 0.09% in people already doing endurance training. For a 20 km ride that takes 30 minutes, 0.09% is about 1.6 seconds. The benefit that did show up was in people who did not exercise regularly.