Vitamin C for Gout

Vitamin C at about 500 mg a day lowers serum uric acid a little: by 0.35 mg/dL on average across 13 randomised trials (Juraschek 2011). In a large trial in 14,641 male physicians, the same dose went with 12% fewer new gout diagnoses over up to 10 years (Juraschek 2022). That is a prevention signal, and a modest one.

For people who already have gout, the picture is different. Two small trials found clinically insignificant changes in urate; in the larger, 500 mg a day lowered urate by 0.23 mg/dL over 8 weeks, against 1.9 mg/dL with allopurinol (Stamp 2013). The 2020 American College of Rheumatology (ACR) guideline conditionally recommends against vitamin C supplements for gout (FitzGerald 2020). Hence the mixed verdict and a rating of 2 out of 5.

The usual explanation is that vitamin C makes the kidneys excrete more uric acid, a uricosuric effect, by competing with urate for reabsorption. Stamp and colleagues (2013) framed their gout trial around this uricosuric effect and found it small in people with gout, even though blood vitamin C levels rose.

A 2026 double-blind crossover trial in 40 adults with high uric acid complicates the story. 600 mg of vitamin C lowered serum uric acid without any change in urinary uric acid excretion or clearance (Enderle 2026), so the fall may come about some other way. In a 2-month trial, vitamin C also raised estimated glomerular filtration rate (GFR, a measure of kidney filtering) compared with placebo (Huang 2005).

A plausible mechanism and a falling blood test are not the same as fewer flares. Gout flares come from urate crystals that have built up in joints over years, and dissolving them needs urate held below 6 mg/dL for a long time (FitzGerald 2020). A fall of 0.2 to 0.5 mg/dL rarely gets anyone there.

Genetics adds doubt. In 106,147 Danish adults, a gene variant that raises vitamin C for life was not linked to urate or hyperuricaemia (Kobylecki 2018), and a larger genetic study found no clear link between vitamin C and gout risk (Qiu 2024). The lower urate seen in people who eat more vitamin C may partly reflect the rest of their diet.

The median dose across the trials in the 2011 meta-analysis was 500 mg a day (Juraschek 2011), and the key trials all used 500 mg: the 2-month trial in 184 adults (Huang 2005), the larger gout trial (Stamp 2013) and the 10-year Physicians' Health Study II (Juraschek 2022). A 2-week crossover trial used 600 mg a day (Enderle 2026).

More is not clearly better. In 1,387 men, uric acid levelled off once vitamin C intake reached 400 to 500 mg a day (Gao 2008). Higher intakes carry a real cost for men: total intakes of 500 to 999 mg a day and supplements of 1,000 mg a day or more were linked to a higher risk of kidney stones (Ferraro 2016).

A 2011 meta-analysis of 13 randomised trials (556 people, median 500 mg a day for 30 days) found serum uric acid fell by 0.35 mg/dL, about 20.8 micromol/L (95% CI -0.66 to -0.03 mg/dL; P = 0.032), with high heterogeneity (Juraschek 2011). A 2021 update with 16 trials and 1,013 people also found a significant fall, larger in placebo-controlled and higher-quality trials (Liu 2021).

The largest single trial, in 184 non-smoking adults, found a fall of 0.5 mg/dL after 2 months, and 1.0 mg/dL in those with the highest starting uric acid (Huang 2005). Most participants in these trials did not have gout, and baseline levels were mostly normal.

In the Physicians' Health Study II, 14,641 men were randomised to 500 mg of vitamin C a day or placebo. New gout diagnoses ran at 8.0 versus 9.1 per 1,000 person-years (HR 0.88, 95% CI 0.77 to 0.99; P = 0.04), with the largest effect in men of normal weight (Juraschek 2022). This was a post hoc analysis with self-reported gout, so it needs repeating.

In 46,994 men followed for 20 years, those taking in 1,500 mg a day or more had a 45% lower risk of gout than those under 250 mg (RR 0.55), and each extra 500 mg a day went with 17% lower risk (Choi 2009). Observational links like these can reflect healthier lifestyles, and two genetic studies did not support a causal effect of vitamin C on urate or gout (Kobylecki 2018; Qiu 2024).

Two small randomised trials, of 29 and 40 people, have tested vitamin C in gout, and both showed clinically insignificant changes in urate (FitzGerald 2020). In the larger, people had an average urate of 8.4 mg/dL; 500 mg a day for 8 weeks lowered it by 0.23 mg/dL, against 1.9 mg/dL when allopurinol was started or increased (P < 0.001), alone or added to allopurinol (Stamp 2013). Reaching the target below 6 mg/dL from that average would take a fall of about 2.4 mg/dL.

A 2021 Cochrane review found no high-quality evidence for or against vitamin C in chronic gout, and rated the 40-person trial at high risk of bias (Andrés 2021). We found no trial that measured whether vitamin C reduces flares, pain or tophi in people with gout.

At 500 mg a day vitamin C is generally well tolerated; the gout trial reported no adverse events (Andrés 2021). High doses can cause diarrhoea, nausea and cramps, and the adult upper limit is 2,000 mg a day (NIH Office of Dietary Supplements).

The bigger concern is kidney stones. In 40,536 men, total vitamin C intakes of 500 to 999 mg a day (median about 700 mg, food and supplements together) were linked to a 29% higher stone risk (HR 1.29), and supplements of 1,000 mg a day or more to a 19% higher risk (HR 1.19); no link was seen in women (Ferraro 2016). A meta-analysis of four studies found the same split between men and women (Jiang 2019). High intakes can also raise urinary oxalate and uric acid, which could contribute to stones in people with kidney problems (NIH Office of Dietary Supplements).

Vitamin C has been taken with allopurinol in a gout trial without reported harm, but it added little urate lowering (Stamp 2013). The NIH Office of Dietary Supplements lists possible interactions with chemotherapy, radiotherapy and statins, and notes that high doses can worsen iron overload in hereditary haemochromatosis.