smartcookie: definitely take a multivitamin, but some people absorb different vitamins better in different forms. You could be deficient even if you take multivitamins, depending on your body’s needs. You should be tested to see what vitamins you are low in so you can focus on exactly what you need. It’s easy to ask your doctor to do the blood test, it’s not expensive and very important to your long-term health. (Also, Vit D for example, being low in your teens increases the risk of osteoporosis later – you want to correct that type of thing while you still can!)
There’s research that people with canker sores are especially low in B vitamins and I needed to take a b-complex vitamin in order to have enough. (They prescribed 50,000 iu of Vit D 1/week – I didn’t want to shock my body like that and figured with 800IU a day (twice the daily requirement) my body will catch up, and BH it worked.) However, everyone has different needs and just because it worked for me doesn’t mean it’s right for you.
Sorry for being so long but I know the terrible feeling of having canker sores. (Going thru it right now – no appetite whatsoever, except chocolate, once in my mouth it hurts too much to enjoy.) Canker sores are a sign that the body is worn out, you need to figure out what that trigger is (it could be low vitamins, stress, allergies, etc.) Feel better!