Condition

COVID-19

COVID-19 is an illness caused by the SARS-CoV-2 virus, ranging from no symptoms to fever, cough and fatigue, and in some people severe lung illness with pneumonia and blood clots. Vitamin D is the most studied supplement for it, yet the one study reviewed found no clear difference in deaths from any cause. That evidence is very limited, and vitamin C, zinc and quercetin have only limited research behind them so far.

Sources: PMID 21735411

Supplements studied: 3
Graded outcomes: 1
Trials: 6
People studied: 10,432

Evidence by supplement

Strong
Moderate
Limited
Very limited

3 supplements

Vitamin D

Vitamin D: outcomes studied for COVID-19
Grade	Outcome	Effect	Size	Studies	People
	All-Cause Mortality No effect		NoneNo effect	1 study	5,806 people
Studies that measured all-cause mortality Vitamin D supplementation for prevention of mortality in adultsCochrane Database Syst Rev · PMID 21735411
	COVID-19 Severity	Improves (the measure goes down)		3 studies	385 people
Studies that measured covid-19 severity Effect of a Single High Dose of Vitamin D3 on Hospital Length of Stay in Patients With Moderate to Severe COVID-19: A Randomized Clinical TrialJAMA · PMID 33595634 Effects of a 2-Week 5000 IU versus 1000 IU Vitamin D3 Supplementation on Recovery of Symptoms in Patients with Mild to Moderate Covid-19: A Randomized Clinical TrialNutrients · PMID 34202578 "Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study"J Steroid Biochem Mol Biol · PMID 32871238
	Length of hospitalization	Improves (the measure goes down)		2 studies	944 people
Studies that measured length of hospitalization Effect of vitamin D supplementation on clinical outcomes in adult patients with COVID-19: A GRADE-assessed systematic review and meta-analysis of randomized controlled trials.Pharmacol Res Perspect · PMID 39350561 The Effect of Vitamin D Supplementation Post COVID-19 Infection and Related Outcomes: A Systematic Review and Meta-Analysis.Nutrients · PMID 39599582
	Need for mechanical ventilation	Changes; see studies		2 studies	2,435 people
Studies that measured need for mechanical ventilation Therapeutic effects of vitamin D supplementation on COVID-19 aggravation: a systematic review and meta-analysis of randomized controlled trials.Front Pharmacol · PMID 38860175 Vitamin D supplementation for managing COVID-19 in patients with vitamin D deficiency: a systematic review and meta-analysis of randomised controlled trials.BMJ Open · PMID 40139702
	C-Reactive Protein (CRP)	Improves (the measure goes down)			1,492 people
	Ferritin	Improves (the measure goes up)			1,492 people
	Hemoglobin	Improves (the measure goes up)			1,492 people
	intensive care unit admission risk	Changes; see studies			4,936 people
	intubation risk	Changes; see studies			4,936 people
	Lymphocyte Count	Improves (the measure goes up)			1,492 people
	Neutrophil Count	Improves (the measure goes up)			1,492 people
	Serum Platelets	Improves (the measure goes up)			447 people

Vitamin C

Vitamin C: outcomes studied for COVID-19
Grade	Outcome	Effect	Size	Studies	People	Studies list
	COVID-19 Severity	Improves (the measure goes down)		2 studies	274 people
Studies that measured covid-19 severity Safety and effectiveness of high-dose vitamin C in patients with COVID-19: a randomized open-label clinical trialEur J Med Res · PMID 33573699 Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical TrialJAMA Netw Open · PMID 33576820

Curcumin

Curcumin: outcomes studied for COVID-19
Grade	Outcome	Effect	Size	Studies	People	Studies list
	COVID-19 Severity	Improves (the measure goes down)		1 study	40 people
Studies that measured covid-19 severity Nano-curcumin therapy, a promising method in modulating inflammatory cytokines in COVID-19 patientsInt Immunopharmacol · PMID 33129099

Key findings

All-Cause MortalityVitamin D

The COVID-19 Prevention and Supportive Care protocol

2 primary supplements · 7 supporting supplements

Vitamin D2,000–4,000 IU daily for prevention (higher if deficient); consult doctor for acute illness
Vitamin C500–1,000 mg daily for prevention; up to 2 g daily during acute illness

See the full protocol

Shop the evidence-backed picks

Support alongside medical care. These supplements are not a treatment for COVID-19. If you are being treated for it, talk to your clinician before adding one: supplements can interact with medicines.

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Studies cited

11 studies from PubMed

Vitamin D supplementation for prevention of mortality in adultsCochrane Database Syst Rev · PMID 21735411
The Effect of Vitamin D Supplementation Post COVID-19 Infection and Related Outcomes: A Systematic Review and Meta-Analysis.Nutrients · PMID 39599582
Effect of vitamin D supplementation on clinical outcomes in adult patients with COVID-19: A GRADE-assessed systematic review and meta-analysis of randomized controlled trials.Pharmacol Res Perspect · PMID 39350561
Vitamin D supplementation for managing COVID-19 in patients with vitamin D deficiency: a systematic review and meta-analysis of randomised controlled trials.BMJ Open · PMID 40139702
Therapeutic effects of vitamin D supplementation on COVID-19 aggravation: a systematic review and meta-analysis of randomized controlled trials.Front Pharmacol · PMID 38860175
"Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study"J Steroid Biochem Mol Biol · PMID 32871238
Effects of a 2-Week 5000 IU versus 1000 IU Vitamin D3 Supplementation on Recovery of Symptoms in Patients with Mild to Moderate Covid-19: A Randomized Clinical TrialNutrients · PMID 34202578
Effect of a Single High Dose of Vitamin D3 on Hospital Length of Stay in Patients With Moderate to Severe COVID-19: A Randomized Clinical TrialJAMA · PMID 33595634
Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical TrialJAMA Netw Open · PMID 33576820
Safety and effectiveness of high-dose vitamin C in patients with COVID-19: a randomized open-label clinical trialEur J Med Res · PMID 33573699
Nano-curcumin therapy, a promising method in modulating inflammatory cytokines in COVID-19 patientsInt Immunopharmacol · PMID 33129099