What is side effect of daily vitamins and minerals?

Side Effects. Side effects of taking a multivitamin include an upset stomach, headache or a bad taste in your mouth.If you take it right before bedtime, it could cause some sleep problems.Most people do not notice any difficulties when taking vitamins. If you take too many, one can have more serious side effects. Discuss with your dr. Before starting a vitamin if you are on medication or have medical issues.