My own purchased supplement: Vitamin D

This is a supplement I take every day. I spend a lot of time indoors, and in the past, I exercised even less than I do now, so I was lacking in sunlight. My immune system became very weak, and after a blood test, my vitamin D levels were less than half of those of an average person. So I kept getting injections and looked for supplements, and this one is quite popular. Since I started taking it, my skin immunity has improved, and I continue to take it regularly. Hehe (I heard that vitamin D is really important for immunity).