Understanding light or irregular periods (oligomenorrhoea)

Irregular periods (oligomenorrhoea) are defined as a full monthly cycle that is less than 21 days or over 35 days, from period to period. Periods might be oscillating between less than 21 and over 35, for example, one cycle being 20 days and the next being 40 days. Periods may be missed.

The ‘menstrual cycle’ is considered medically to be from Day 1 of your period to Day 1 of your next period, though in some countries, people say ‘cycle’ and mean their period.

Symptoms of irregular periods

  • Very light pink or brown discharge or blood, but no real period
  • Cramping and pain, but not getting any bleeding
  • May have stopped the pill but period doesn’t come
  • Not pregnant
  • Had a pregnancy but periods didn’t return
  • Had COVID, and periods didn’t return

When irregular periods are normal

When a young person starts getting periods (menarche), it’s usual for periods to be irregular for a year or so. In perimenopause, periods can be irregular for a few years, with heavier bleeding and sometimes two periods in a month.

When there is the absence of a period for three months in a row, this is called amenorrhoea.

Causes of irregular periods

‍Some factors influencing periods include thyroid function, stress levels, nutrient levels and the amount of exercise undertaken​1​. Hormonal imbalances or fluctuations can create irregular cycles.

Excess androgens

Testosterone and other androgens can interfere with ovulation, creating irregular cycles. A major cause of irregular periods is polycystic ovarian syndrome (PCOS).

High prolactin

‍Hyperprolactinaemia (high prolactin) can cause irregular periods or skipped periods, low libido, tender breasts, headaches, acne breakouts, facial hair growth and vaginal symptoms such as vaginal dryness.

High prolactin may be confused with PCOS. Possible causes of elevated prolactin include thyroid dysfunction, benign tumours of the pituitary, an abundance of oestrogen, some medicines like SSRI antidepressants, proton pump inhibitors for acid reflux, antipsychotic drugs, under eating​2​, alcohol use, and stress.

Low thyroid (hypthyroidism)

When the thyroid gland is underactive, producing insufficient amounts of thyroid hormone, ovulation is affected, resulting in a lack of progesterone production. A standard thyroid screening may not be enough to check for thyroid function, so see a practitioner for guidance and thorough testing.

Toxin exposure

Herbicides, pesticides, heavy metals, food preservatives, colours and additives, solvents, flame retardants, and pollution interfere with hormonal functioning, and can lead to irregular periods. Some people don’t tolerate higher levels of these chemicals and toxins, leading to symptoms.

Gut health, microbiome and digestion

Imbalanced gut flora can impact hormone regulation and clearance, nutrient uptake, food breakdown, and lead to inflammation. Ensuring the digestive tract is happy can be an important part of understanding and treating irregular periods.

Treating irregular periods

First is the investigation phase, where it’s important to work out why periods have become irregular and rule out serious medical concerns. A practitioner may do a pelvic examination, take a swab for infections, and if necessary, refer to a gynaecologist.

Medical investigations may include blood tests, pelvic scans, ultrasounds, and in some cases, a laparoscopy or hysteroscopy to investigate the pelvic cavity and organs. A medical doctor may prescribe the oral contraceptive pill or other medications.

An integrative or holistic practitioner will be seeking the underling causes and any contributing factors, taking a comprehensive health history, including menstrual cycles, genetics​3​ and family history.

Treatment may include changes to diet and lifestyle, herbal medicines to balance hormones​4​, improving the quality of the vaginal and gut microbiome, restoring thyroid function, nutritional support and ensuring only essential medications are required.


  1. 1.
    Awdishu S, Williams NI, Laredo SE, De Souza MJ. Oligomenorrhoea in Exercising Women. Sports Medicine. Published online December 2009:1055-1069. doi:10.2165/11317910-000000000-00000
  2. 2.
    Zhou X, Yang X. Association between obesity and oligomenorrhea or irregular menstruation in Chinese women of childbearing age: a cross-sectional study. Gynecological Endocrinology. Published online August 12, 2020:1101-1105. doi:10.1080/09513590.2020.1803823
  3. 3.
    Andreeva V. Molecular-genetic markers in the genesis of oligomenorrhea in adolescents. Journal of Pediatric and Adolescent Gynecology. Published online April 2023:251. doi:10.1016/j.jpag.2023.01.198
  4. 4.
    Moini Jazani A, Hamdi K, Tansaz M, et al. Herbal Medicine for Oligomenorrhea and Amenorrhea: A Systematic Review of Ancient and Conventional Medicine. BioMed Research International. Published online 2018:1-22. doi:10.1155/2018/3052768
  5. 5.
    He Y, Zheng D, Shang W, et al. Prevalence of oligomenorrhea among women of childbearing age in China: A large community-based study. Womens Health (Lond Engl). Published online January 2020:174550652092861. doi:10.1177/1745506520928617

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)