The oral contraceptive pill

The oral contraceptive pill (OCP) is a form of contraception taken orally once per day to prevent pregnancy. The pill can also be used to help to manage hormone fluctuations that can cause premenstrual syndrome (PMS), acne, or other conditions such as polycystic ovarian syndrome (PCOS)​1​ and endometriosis.

The combined oral contraceptive pill (COCP) contains progestin and various forms of oestrogen. The combined pill is different to the mini pill, which is just one hormone (progestin, a synthetic progesterone).

The OCP comes in a packet with the days of the week on it, so you can remember what day you are up to.

How you take the pill

The OCP has a 7-day sugar pill dose per 21 hormone pills (for a 28-day cycle). These sugar pills do not contain hormones, and cause what’s known as ‘breakthrough bleeding’. This bleed is meant to look and feel like a period, but it is not a ‘real’ period because you haven’t ovulated.

The hormone cascade that causes ovulation and a menstrual period is blocked by the pill, and instead a false ‘period’ occurs. This decision was taken to make pill users feel more comfortable and ‘normal’.

But, it’s up for debate what is safer – to just keep running together pill packets until you start breakthrough bleeding, or to stop and start as per the directions. Your ‘period’ on the pill is actually called a withdrawal bleed.

You can run several pill packets together without harm, though you may get breakthrough bleeding after one or two cycles, requiring a full withdrawal bleed to ‘clear’ your uterus of endometrial lining.

The hormones are all very slightly molecularly different from each other (to allow patents). This is why if one doesn’t work for you, another one might.

The pill and your sex drive (remember that old thing?)

Ironically, the pill is famous for causing a loss of libido. The pill can also cause some users to become emotionally numb.

The pill and the gut and vaginal microbiome

The pill changes the gut microbiome, but research has been mixed about its influences. One study found a minor decrease in microbial diversity (undesirable), while another found increases in certain types of bacteria.​2,3​ The pill also increases the risk of developing inflammatory bowel disease.​4,5​ The gut-brain axis may be linked with OCP use, potentially being responsible for some of the unwanted mental and emotional side-effects of the pill​6​.

The pill affects the vaginal microbiome​7​. It protects (slightly) against bacterial vaginosis (BV), but increase the risk of yeast infections.​8​ Many forms of contraceptives impact the vaginal microbiome​9​.


  1. 1.
    Eyupoglu ND, Caliskan Guzelce E, Acikgoz A, et al. Circulating gut microbiota metabolite trimethylamine N‐oxide and oral contraceptive use in polycystic ovary syndrome. Clinical Endocrinology. Published online October 6, 2019:810-815. doi:10.1111/cen.14101
  2. 2.
    Mihajlovic J, Leutner M, Hausmann B, et al. Combined hormonal contraceptives are associated with minor changes in composition and diversity in gut microbiota of healthy women. Environmental Microbiology. Published online May 6, 2021:3037-3047. doi:10.1111/1462-2920.15517
  3. 3.
    Hua X, Cao Y, Morgan DM, et al. Longitudinal analysis of the impact of oral contraceptive use on the gut microbiome. Journal of Medical Microbiology. Published online April 27, 2022. doi:10.1099/jmm.0.001512
  4. 4.
    Ortizo R, Lee SY, Nguyen ET, Jamal MM, Bechtold MM, Nguyen DL. Exposure to oral contraceptives increases the risk for development of inflammatory bowel disease: a meta-analysis of case-controlled and cohort studies. European Journal of Gastroenterology & Hepatology. Published online September 2017:1064-1070. doi:10.1097/meg.0000000000000915
  5. 5.
    Sanagapalli S, Ko Y, Kariyawasam V, et al. The association between new generation oral contraceptive pill and the development of inflammatory bowel diseases. Intest Res. Published online 2018:409. doi:10.5217/ir.2018.16.3.409
  6. 6.
    Kheloui S, Smith A, Ismail N. Combined oral contraceptives and mental health: Are adolescence and the gut-brain axis the missing links? Frontiers in Neuroendocrinology. Published online January 2023:101041. doi:10.1016/j.yfrne.2022.101041
  7. 7.
    Brooks JP, Edwards DJ, Blithe DL, et al. Effects of combined oral contraceptives, depot medroxyprogesterone acetate and the levonorgestrel-releasing intrauterine system on the vaginal microbiome. Contraception. Published online April 2017:405-413. doi:10.1016/j.contraception.2016.11.006
  8. 8.
    Kazi YF, Saleem S, Kazi N. Investigation of vaginal microbiota in sexually active women using hormonal contraceptives in Pakistan. BMC Urol. Published online August 18, 2012. doi:10.1186/1471-2490-12-22
  9. 9.
    Bakus C, Budge KL, Feigenblum N, Figueroa M, Francis AP. The impact of contraceptives on the vaginal microbiome in the non-pregnant state. Front Microbiomes. Published online January 30, 2023. doi:10.3389/frmbi.2022.1055472

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Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

  • International Society for the Study of Vulvovaginal Disease (ISSVD)
  • International Society for the Study of Women's Sexual Health (ISSWSH)
  • National Vulvodynia Association (NVA) Australia
  • New Zealand Vulvovaginal Society (ANZVS)
  • Australian Traditional Medicine Society (ATMS)