There was a period when I seemed to get a cold every couple of weeks. I was really run down. My acupuncturist recommended that I take Astragalus every three times a day for a couple of months to rebuild my immune system. I have no idea how it works, but it did make a huge difference. I stopped getting colds. (And when I do feel I'm about to get one, the acute remedy is Gan Mao Ling (see separate review.)) Now that I'm feeling better, I take two capsules just once a day as part of my overall vitamin regimen.