What is the recommended dosage for Vitamin D?

General: 600-800 IU/day; Immune Support: 1,000-2,000 IU/day; Deficiency Correction: 4,000-5,000 IU/day (under medical supervision)

What are the side effects of Vitamin D?

Potential side effects include: Hypercalcemia at very high doses (nausea, vomiting, weakness), Kidney stones with excessive long-term use, Constipation, Metallic taste.

What is vitamin D and how does it support immune function?

Vitamin D is a fat-soluble vitamin that plays a critical role in both innate and adaptive immunity. Immune cells express vitamin D receptors, and vitamin D influences antimicrobial peptide production (cathelicidin), T-cell differentiation, and inflammatory cytokine regulation.

What dosage of vitamin D has been studied for immune health?

Clinical trials have used vitamin D3 at doses of 400–4,000 IU per day. Meta-analyses suggest that daily or weekly supplementation (not bolus dosing) is more effective for reducing respiratory infection risk, particularly in individuals with baseline deficiency.

What are the potential side effects of vitamin D supplementation?

Vitamin D is generally safe at doses up to 4,000 IU per day for adults. Excessive intake can cause hypercalcemia, leading to nausea, weakness, and kidney problems. Blood levels (25-hydroxyvitamin D) should be monitored when taking doses above 2,000 IU per day.

Vitamin D

vitamin

Also known as: Cholecalciferol, Vitamin D3, Ergocalciferol, Calciferol

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About

Vitamin D is a fat-soluble secosteroid hormone that modulates both innate and adaptive immune responses. It maintains epithelial barrier integrity, boosts production of antimicrobial peptides (cathelicidin LL-37 and defensins), and regulates T-cell and macrophage function. The VITAL trial demonstrated a 22% reduction in autoimmune disease risk with supplementation.

How It Works

Modulates both innate and adaptive immune responses by maintaining epithelial barrier integrity and boosting production of antimicrobial peptides (cathelicidin LL-37 and defensins); regulates T-cell and macrophage function.

Evidence For Conditions

Condition	Grade	Studies	Participants
Upper Respiratory Tract Infections	A	40	30000	View →
Autoimmune Conditions	A	3	25871	View →
Immune Aging (Immunosenescence)	B	10	5000	View →

Side Effects

Hypercalcemia at very high doses (nausea, vomiting, weakness)
Kidney stones with excessive long-term use
Constipation
Metallic taste

Drug & Supplement Interactions

Thiazide diuretics (may increase risk of hypercalcemia)
Corticosteroids (reduce vitamin D absorption and metabolism)
Orlistat and cholestyramine (reduce fat-soluble vitamin absorption)
Statins (vitamin D may affect statin metabolism)

Always inform your healthcare provider about all supplements you take.

Related Ingredients

Vitamin A Vitamin B6 Vitamin C Vitamin E

Quick Facts

Dosage: General: 600-800 IU/day; Immune_Support: 1,000-2,000 IU/day; Deficiency_Correction: 4,000-5,000 IU/day (under medical supervision)
Forms: capsule softgel liquid drops tablet gummy
Natural Sources: Sunlight, Fatty fish (salmon, mackerel), Egg yolks, Fortified milk, Mushrooms (UV-exposed)
Upper Limit: 4,000 IU/day (100 mcg)
Best Time: With a meal containing fat for better absorption

Evidence Summary

Upper Respiratory Tract Infections A

Autoimmune Conditions A

Immune Aging (Immunosenescence) B

FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.