"To take a multivitamin" means to consume a supplement that contains different essential vitamins and minerals in order to support overall health and fill in any nutritional gaps in your diet. Full definition
Play it safe by taking a multivitamin with at least 400 milligrams of folic acid even if you're not pregnant or trying (half of all pregnancies are unplanned!) (health.com)
I started taking the multivitamin supplement not too long ago, maybe a week or so (it contains vitamins A, D and C). (perfecthealthdiet.com)
It might be your mother, your brother, or even you, but anyone who takes a multivitamin swears by it and knows that it holds healthy benefits. (dogfoodinsider.com)