It seems that many(most?) people talk about “how much” vitamin D they take. This is nonsense.
The important issue is not how much we take, but how much we have in our blood. Unless you have your blood checked for vitamin D you have absolutely NO IDEA whether you are deficient or not.
And, another thing—the optimal blood level for vitamin D is actually quite a bit higher than the “recommended” level. Don’t be afraid of vitamin D supplements. Do some research and you will learn that overdosing on this vitamin is almost impossible, and has seldom ever been reported—even with enormous supplement intake.
Take this for what it is worth, but you need to know that an optimal vitamin level is absolutely necessary if you want to be healthy.
(The writer is 80 years old, seldom, if never sick, and has been taking thousands of IU of vitamin D3 for many years.)
About 13rd the US and world population is deficient in Vitamin D. Even people living in the tropics frequently are as it is harder for dark skin to allow the sun engendered D to absorb from the skin into the body. This is why the death rate of dark-skinned people including American Indians has been 2.5 times the rate for light-skinned people in this country. When calculating how much Vitamin D a person may need, you have to include time of year, location like north or south, and length of sun exposure. People in Florida and other southern location frequently stay inside for the air conditioning in Summer which probably explains aome increases in Covid in some southern states in Summer.
I guess by “writer” you mean me. Actually I am 84, and until Summer 2020 I was only taking the amount of Vitamin D in my twice daily one-a-day multi vitamin and mineral tablets, about 800IU daily. My health had been generally good because have been taking a targeted array of supplements for over 50 years. Then as explained in my Comment here I increased my D intake based on new Covid information and my on-line research. A lot of the newest research now recognizes the level of Vitamin D needed for a healthy immune system is much higher than what is needed for bone health and rickets. I have asked others living in the mid-Atlantic zone about their D intake. A 200 lb 5’11” man said his doctor gives him a 40,000IU D shot once a week. A tall chunky, not fat, black woman said her doctor put her on 10,000IU a decade ago. Two frail elderly black women told me their doctor recommended 5000IU daily. Using the information here and in my Comment, you can make a rough estimate of what to take, but get in to have your blood tested to fine tune your intake. If you have been using a lot for a while you might need to cut back a bit. Good luck, but do test.