ingestible · for post-viral recovery (long covid)
Vitamin D3
Reviewed by the Nimbera editorial team · Last updated May 2026
How to use
Get vitamin D levels tested first (25-OH vitamin D blood test). If deficient (under 30 ng/mL), take 2,000-4,000 IU D3 daily with K2 (100 mcg MK-7) to support calcium metabolism. Retest after 12 weeks. Take with a fat-containing meal for best absorption.
How it works
Vitamin D deficiency is consistently more prevalent in long COVID patients and correlates with symptom burden. Vitamin D modulates immune function, reduces inflammatory cytokine production, supports mitochondrial health, and regulates neurological processes linked to fatigue and brain fog.
Where to buy
Pharmacies, health stores, online. Brands: Thorne D3/K2, Nordic Naturals Vitamin D3, Garden of Life Vitamin D3.
Typical cost: $10-$25 per month
Safety notes
Toxicity possible at very high doses - do not exceed 10,000 IU/day without medical supervision. Get blood levels tested before and during supplementation. People with granulomatous diseases (sarcoidosis) or hyperparathyroidism should consult a doctor before supplementing.
Drug & supplement interactions
- Always tell your doctor or pharmacist about any supplements you take.
- Interactions can occur with prescription medications, blood thinners, and immunosuppressants.
- Herbal remedies can affect how the body absorbs or metabolises drugs.
- Check drugs.com interactions checker before starting.
Clinical source
PubMed - Benskin et al. 2024This information is compiled from primary clinical literature and is for informational purposes only. It is not a substitute for professional medical advice. Read our full disclaimer.