Effects of oral contraceptives on vitamins B6, B12, C, and folacin

J Nurse Midwifery. 1984 Nov-Dec;29(6):386-90. doi: 10.1016/0091-2182(84)90169-1.


PIP: This article examines the effects of oral contraceptives (OCs) on the metabolism of vitamin B6, folacin, vitamin B12, and vitamin C and outlines educational strategies through which nurse-midwives can improve their clients' nutritional health. Evidence of vitamin B6 deficiency has been found among combination OC users in numerous studies. Derangement of tryptophan metabolism occurs within 1 month of initiation of OC use. OCs also may cause a deficiency of pyridoxal phosphate, a coenzyme needed for the tryptophan-nicotinic acid pathway. It is recommended that OC users take 1-1.5 mg/day of supplemental vitamin B6; new OC users should take 5 mg/day until plasma levels of 1.5-2 mg have been achieved. It has also been noted that OCs impair folacin metabolism, as evidenced by folacin deficiency in serum and an increase in urinary formiminoglutamic acid secretion. It is generally ageed that folacin, which plays a critical role in fetal development, can become deficient in late pregnancy and in women who become pregnant shortly after discontinuing longterm OC use. OCs further influence serum B12 concentrations and the possiblity of iron deficiency anemia. Among patients who are well nourished and nonsmokers, OC use does not appear to jeopardize vitamin C levels. An assessment of a patient's nutritional health should begin with a demographic evaluation focused on her age, parity, alcohol and nicotine consumption, and use of medications and vitamins. Next, a dietary evaluation should be made by having the patient record everything she eats during the following week. It should be remembered that adolescents, lactating women, those with repeated pregnancies closely spaced, and women who are chemically dependent have greater nutritional needs than normal. Nutritional counseling is particularly needed by OC users, who may be deficient in 1 or more of the essential vitamins. Nutritional counseling should be an ongoing part of any comprehensive patient-teaching program.

MeSH terms

  • Ascorbic Acid / metabolism
  • Contraceptives, Oral / pharmacology*
  • Female
  • Folic Acid / metabolism
  • Humans
  • Lactation
  • Pregnancy
  • Pyridoxine / metabolism
  • Vitamin B 12 / metabolism
  • Vitamins / metabolism*


  • Contraceptives, Oral
  • Vitamins
  • Folic Acid
  • Pyridoxine
  • Vitamin B 12
  • Ascorbic Acid