Numerous multivitamin preparations are marketed, with little standardization of formulas. Useful multivitamin preparations should contain only essential vitamins (those for which there is a recommended daily dietary allowance [RDA]).
When a single vitamin deficiency is evident, other vitamin deficiencies (clinical or subclinical) often accompany it. Therapeutic multivitamin preparations
(see Dosage and Administration)may, therefore, be useful in these patients. Therapeutic multivitamins may also be indicated in pathologic conditions in which nutritional requirements are greatly increased (e.g., alcoholism, hyperthyroidism, severe illness or injury, cachexia) or in conditions in which absorption, utilization, or excretion of vitamins is abnormal (including malabsorption syndromes). Therapeutic multivitamins should not be used as dietary supplements, and medical supervision is important when these preparations are given.
An adequate amount of vitamins and minerals usually is obtained from a well-balanced diet, and healthy individuals consuming such a diet can expect no benefit from additional vitamins. Supplementary multivitamin preparations
(see Dosage and Administration)may be used to assure an adequate supply of vitamins in patients with poor dietary habits or temporarily decreased dietary intake. Preparations containing 100-150% of the RDA may be useful in patients with severely restricted food intake. Whenever possible, poor dietary habits should be corrected. Vitamin and mineral supplements may be required to meet temporarily increased demand (e.g., during pregnancy and lactation) or to ensure proper growth of infants and children. Patients undergoing hemodialysis may require vitamin and mineral supplements to compensate for increased losses.
The vitamin combination chosen should fit the needs of the individual patient. In selecting a multivitamin, it should be remembered that increased intake of certain vitamins or nutrients increases the demand for other vitamins. Also, some vitamins (especially vitamins A and D) and many minerals may be toxic in large doses, and dosage of multivitamin preparations containing these agents should take the patient's dietary intake into account. There is a potential danger in administering more than the RDA of folic acid to patients with undiagnosed anemia because folic acid may obscure the diagnosis of pernicious anemia by alleviating hematologic manifestations of the disease while allowing neurologic complications to progress.