Well if in blood test you are diagnosed with vitamin deficiency, it's treated with pills. So they are effective.
1. Take it together with food (containing fat) so it gets dissolved. 2. For each micronutrient check if it's in the best available form, and big enough dose.
Sometimes vitamin deficiency is treated will pills. I know people who have to get vitamin shots because pills don't work for their condition.
I always tell people treat vitamin deficiency with a healthy diet, if that doesn't work you have a gut problem and pills won't fix it either. I'm not a doctor, but it is a reasonable claim.
1. Take it together with food (containing fat) so it gets dissolved. 2. For each micronutrient check if it's in the best available form, and big enough dose.