COVID severity tied to vitamin D level
<20 more likely to be in the ICU and die
>30 More likely to have milder case.
Next: Get your Vitamin D levels checked
Last: upper daily limit with no MD supervision
https://www.medpagetoday.com/meetingcoverage/asbmr/88586

Get your level checked, try to get your level to 50 ng/ml or higher with your doctor's help.

Normal Vitamin D level range is 30-100 ng/ml
UK and US recommended daily dose of 400-800 ius of D will not get your level where it needs to be.
Next: Upper dose with no MD supervision

Dr Seheult, pulmonologist says 4,000 ius of Vitamin D is upper daily limit to take with no MD supervision. See the 12:55 mark

If You Get COVID 19: Optimize Immune System (Vitamin D, Monoclonal Antibodies, NAC, Quercetin etc.) Jan 2, 2021

Vitamin D studies https://c19vitamind.com 

What Vitamin D level is optimal? See this chart in the video at 12:58 mark
Vitamin D and COVID 19: The Evidence for Prevention and Treatment of Coronavirus (SARS CoV 2)

VITAMIN D FOR ALL
Letter signed by 200 doctors
https://vitamindforall.org/letter.html 

According to these 200 MDs, 4,000 ius can barely get you to the Vitamin D sufficiency level. Get tested, follow your MD. US gov experts only recommend 400-600 ius per day.
The UK NHS website only recommends 400 ius per day

https://vitamindforall.org/letter.html 

Different people need different amounts of Vitamin D to achieve a protective level. The MD in this video discovered that his level was only 11, in the summertime after a week at the beach. He is involved with the Vitamin D For All website. h/t @naomirwolf

Great way to figure the dose of Vit D you need without an MD, but you really should have an MD check your level. If taking more than 4,000 iu per day, you need MD advice.
https://vatsalthakkar.com/vitamin-d-calculator.html
For who are obese, this calculator helps figure a dose factoring in BMI.

Great discussion of Vitamin D studies on prevention and treatment of COVID, vitamin D reduces all cause mortality etc.

There are 26 vitamin D studies expertly discussed and clearly explained here by Pulmonologist and Prof Dr Seheult. Vitamin D is of great interest to a Pulmonologist in the prevention & treat of COVID
(Several studies discussed in previous video as well)