Protocols › Vitamin C

Vitamin C for blood pressure

Goal: To lower blood pressure a little, as short trials of vitamin C found.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 3 Nov 2026
Dose

A median of 500 mg a day in 29 trials, and of 757.5 mg a day in 20 trials of a 2023 review.[1][2]

How long

A median of 8 weeks in one review and 6 weeks in the other.[1][2]

What studies found

Systolic pressure fell by 3.84 mmHg and diastolic by 1.48 mmHg (29 trials); by 4.85 mmHg systolic in people with high blood pressure.[1] A 2023 review of 20 trials in 890 adults: systolic minus 3.0 mmHg, minus 4.6 mmHg in diabetes.[2] Two large trials of 500 mg a day for 8 and 9.4 years found no fewer heart attacks or strokes.[3][4]

Ask a doctor first

High doses can cause diarrhea, nausea and stomach cramps. The US upper limit for adults is 2,000 mg a day, and lower for children.[5] In men, supplements of 1,000 mg a day or more went with more kidney stones.[6] Ask a doctor or pharmacist first if you have kidney stones, kidney disease or hemochromatosis, or are in cancer treatment.[5] People who take a statin for cholesterol should also ask first.[5]

References

  1. Effects of vitamin C supplementation on blood pressure: a meta-analysis of randomized controlled trials. Juraschek SP, Guallar E, Appel LJ, Miller ER 3rd Am J Clin Nutr, 2012. PMID 22492364
  2. Vitamin C supplementation showed greater effects on systolic blood pressure in hypertensive and diabetic patients: an updated systematic review and meta-analysis of randomised clinical trials. Lbban E, Kwon K, Ashor A, Stephan B, Idris I, Tsintzas K, et al. Int J Food Sci Nutr, 2023. PMID 37791386
  3. Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. Sesso HD, Buring JE, Christen WG, Kurth T, Belanger C, MacFadyen J, et al. JAMA, 2008. PMID 18997197
  4. A randomized factorial trial of vitamins C and E and beta carotene in the secondary prevention of cardiovascular events in women: results from the Women's Antioxidant Cardiovascular Study. Cook NR, Albert CM, Gaziano JM, Zaharris E, MacFadyen J, Danielson E, et al. Arch Intern Med, 2007. PMID 17698683
  5. Vitamin C: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  6. Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones. Ferraro PM, Curhan GC, Gambaro G, Taylor EN Am J Kidney Dis, 2016. PMID 26463139