What the experts say:
Keep it simple. The more ingredients there are in a supplement combo, the more chance that one of them will not be the right amount.
Consider a supplement combo tailored to your gender and age.
Multivitamins often contain little iron, and ones for seniors give more calcium and vitamin D than products aimed at younger adults.
Take vitamin D with dinner. It is absorbed more when consumed with the largest meal.
Watch out for vitamin K. It promotes clotting and can interfere with common heart medicines and blood thinners.
Current and former smokers are advised to avoid multivitamins with lots of beta-carotene or vitamin A as it raises lung cancer risk in them.
For cancer patients, vitamins C and E might reduce the effectiveness of certain types of chemotherapy.
People having surgery should know that some vitamins can affect bleeding and response to anaesthesia.