Headaches are not only an unintended consequence of vitamins A, B, and C. Excessive use of any vitamin, mineral, or multivitamin may result in vitamin overdose symptoms. In severe situations, this is known as hypervitaminosis, and it happens when the body stores unusually large levels of vitamins, causing toxicity. Increasing your intake of vitamin B complex can help you lose weight since these vitamins increase your appetite, which is generally suppressed during a fever. Because calcium absorption is reduced during a fever, taking a calcium supplement may be advantageous.