Prescription ·Strong evidence ·Reviewed May 2026
Combined oral contraceptives (COCs) contain synthetic estrogen (usually ethinyl estradiol 20–35 mcg) and a progestin component. They are primarily used for contraception but are also prescribed for menstrual regulation, dysmenorrhea, endometriosis, acne, and polycystic ovary syndrome (PCOS). They are among the most widely used medications worldwide with an extensive safety record when appropriately prescribed.
The bottom line
Evidence rating strong. Most-documented uses: highly effective contraception (>99% with perfect use), menstrual cycle regulation, reduced dysmenorrhea and menstrual blood loss. 10 sources indexed (2020–2025), with 14 interaction records on file.
Core mechanism
The progestin component suppresses the LH surge, preventing ovulation, while both the estrogen and progestin thicken cervical mucus (impeding sperm penetration), thin the endometrial lining (reducing implantation potential), and alter tubal motility. The estrogen component also suppresses FSH, preventing follicular development, and stabilizes the endometrium to prevent breakthrough bleeding.
Can be taken with or without food. Take at the same time each day for optimal efficacy. Vomiting or diarrhea within 2 hours of taking may reduce effectiveness.
Nutrients this medication can lower over time, and what to replace.
Estrogen-containing contraceptives can increase vitamin B6 turnover and lower circulating PLP in susceptible users.
Long-term oral contraceptive use is associated with lower measured B12 status, likely from altered binding proteins and absorption dynamics.
Estrogen-progestin contraceptives can lower folate status through altered metabolism and increased requirement in some users.
Oral contraceptives are associated with lower magnesium status in some users, likely through altered renal handling and demand.
Estrogen-containing contraceptives can modestly lower zinc status, likely through altered hepatic protein synthesis and increased losses.
Some users show lower plasma vitamin C during chronic oral contraceptive use, likely from increased oxidative turnover.
Estrogen-containing contraceptives can modestly alter selenium handling and lower functional selenium status in some users.
St. John's Wort induces CYP3A4, dramatically reducing levels of ethinyl estradiol and progestins. This causes contraceptive failure and unintended pregnancy. The FDA and WHO list this as a contraindication.
Recommendation: Do NOT take St. John's Wort with oral contraceptives. Use alternative contraception (non-hormonal) if taking SJW. Multiple documented cases of unintended pregnancy.
A systematic review and meta-analysis of 17 studies found that women using combined oral contraceptives had significantly lower serum and red-cell folate than non-users. This matters most for women who may conceive shortly after stopping the pill, because low folate at conception raises neural tube defect risk.
Recommendation: Take a daily folate-containing multivitamin (400-800 mcg of folic acid or 5-MTHF) while on combined oral contraception, especially in the year before any planned pregnancy. The folate can be taken with or without the pill.
Methylfolate (5-MTHF) is the active circulating form of folate and is the preferred supplement for women on combined oral contraceptives, particularly those with MTHFR variants. COCs lower serum and red-cell folate, and 5-MTHF restores levels quickly without dependence on hepatic conversion of folic acid.
Recommendation: Take methylfolate 400-800 mcg daily while on combined oral contraception, especially if you plan to conceive after stopping. Methylfolate can be taken at any time of day, with or without the pill.
Combined oral contraceptives lower plasma pyridoxal-5-phosphate (active vitamin B6) and can contribute to low mood, irritability, and nausea. In a controlled trial, B6 50 mg/day reduced these side effects in Cambodian women using oral contraception.
Recommendation: Consider a daily B6 supplement (25-50 mg as pyridoxine or P5P) while on combined oral contraception, particularly if you experience low mood, irritability, or nausea. Take with or without food, at any time of day.
Combined oral contraceptives are associated with lower serum vitamin B12 levels in multiple observational and review studies. Although clinical deficiency is uncommon, the drop can become meaningful in vegetarians, vegans, and long-term pill users, and matters for any planned pregnancy.
Recommendation: Consider a daily B12 supplement (250-1000 mcg as methylcobalamin or cyanocobalamin) while on combined oral contraception, especially if you eat little animal protein or have been on the pill for many years.
Methylcobalamin is the active circulating form of vitamin B12 and is depleted along with other B vitamins during combined oral contraceptive use. Restoring B12 is particularly important for one-carbon metabolism, energy, and pre-conception health.
Recommendation: Take methylcobalamin 500-1000 mcg daily while on combined oral contraception, particularly with concurrent methylfolate. Either is best taken in the morning with breakfast.
Combined oral contraceptives lower plasma and platelet vitamin C levels and increase oxidative stress, partly because estrogen induces hepatic enzymes that increase vitamin C turnover. Modest daily supplementation restores levels and antioxidant capacity.
Recommendation: A daily multivitamin or 250-500 mg vitamin C is reasonable for women on combined oral contraception. Avoid very high doses (above 1000 mg/day) at the same time as the pill, since vitamin C may transiently raise ethinyl estradiol levels.
Combined oral contraceptives reduce serum levels of lipid-soluble antioxidants including alpha-tocopherol and coenzyme Q10. In a controlled study of premenopausal women, OC use significantly lowered both. Replenishing vitamin E helps offset COC-associated oxidative stress.
Recommendation: A daily multivitamin or 100-200 IU of mixed tocopherols is reasonable for women on combined oral contraception. Take with food containing fat for absorption.
Combined oral contraceptive use significantly decreases serum coenzyme Q10 levels in premenopausal women, mirroring the drop seen with statins. Although clinical consequences are not fully defined, restoring CoQ10 supports mitochondrial function and antioxidant capacity.
Recommendation: Consider CoQ10 100-200 mg daily (ubiquinone or ubiquinol) while on combined oral contraception, particularly if you have fatigue, exercise intolerance, or take other CoQ10-depleting medications. Take with a meal containing fat.
Combined oral contraceptive use is associated with lower serum magnesium and altered mineral status in observational studies, contributing to fatigue, muscle cramps, and headaches in some women. Magnesium supplementation restores levels and may improve tolerability.
Recommendation: Use a modest magnesium supplement only as needed to meet intake goals while on combined oral contraception, especially if you have headaches, cramps, or mood symptoms. Best taken in the evening for sleep benefit.
Multiple observational studies show that combined oral contraceptive users have lower serum zinc compared with non-users. The clinical impact is usually modest, but matters for immunity, skin, and any planned pregnancy.
Recommendation: A daily multivitamin or zinc 10-15 mg is reasonable for women on combined oral contraception. Take with food to reduce nausea, and not at the same time as iron or calcium for best absorption.
Combined oral contraceptive use is associated with lower serum selenium and reduced glutathione peroxidase activity in several studies, contributing to lower antioxidant capacity. Selenium adequacy also supports normal thyroid hormone metabolism, which is relevant because COCs raise thyroid-binding globulin.
Recommendation: A daily multivitamin or 55-100 mcg of selenium is reasonable for women on combined oral contraception. Brazil nuts (1-2 per day) provide a natural dietary source.
Search all 14 interaction records for Combined Oral Contraceptive →
Numbered references. Citations throughout the page link here.
Piacenti I, Tius V, Viscardi MF et al.. Dienogest vs. combined oral contraceptive: A systematic review and meta-analysis of efficacy and side effects to inform evidence-based guidelines. Acta obstetricia et gynecologica Scandinavica. 2025
Watling CZ, Sweetland S, Wojt A et al.. Oral contraceptive use and risk of liver cancer: a population-based study, systematic review, and meta-analysis. The Lancet. Oncology. 2025
Nolan D, McNulty KL, Manninen M et al.. The Effect of Hormonal Contraceptive Use on Skeletal Muscle Hypertrophy, Power and Strength Adaptations to Resistance Exercise Training: A Systematic Review and Multilevel Meta-analysis. Sports medicine (Auckland, N.Z.). 2024
Brabaharan S, Veettil SK, Kaiser JE et al.. Association of Hormonal Contraceptive Use With Adverse Health Outcomes: An Umbrella Review of Meta-analyses of Randomized Clinical Trials and Cohort Studies. JAMA network open. 2022
Leelakanok N, Methaneethorn J. A Systematic Review and Meta-analysis of the Adverse Effects of Levonorgestrel Emergency Oral Contraceptive. Clinical drug investigation. 2020
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