Supplements, such as a multivitamin, are available over the counter and can be bought in nearly every supermarket or drug store. Just because they do not require a prescription does not mean you shouldn’t discuss with your doctor whether you be taking one.
Certain supplements may interfere with medications and need to be spaced out appropriately.
It is the position of the Academy of Nutrition and Dietetics that food be the primary vessel for nutrition. If you are concerned about missing nutrients in your diet, speak with a dietitian about balanced eating.
My best advice is to eat well–rounded meals with plenty of variety to maximize your nutrient intake from foods, and to speak with a doctor before starting and/or stopping a supplement regimen.