Bleeding- Irregular or long cycles

1. Irregular menstrual cycles–  Note- It’s quite usual to have irregular cycles (i.e. not between 21 and 35 days in length) for a few years after puberty and before the menopause [1]. Your menstrual cycle can also be disturbed if you change your method of contraception, are pregnant, or you have a hormonal imbalance.

If you are between 20 and 45 years old, an irregular cycle (under or over 21-35 days in length) may be caused by hormonal medications; Polycystic Ovary Syndrome (PCOS); being under, or over-weight; stress; a hormonal imbalance; or a mild thyroid condition [1].

2. Menstrual cycles of over 35 days (long cycles)– The medical term is ‘oligomenorrhoea‘- Long cycles usually represent anovulation (a lack of ovulation). The most common cause is Polycystic Ovary Syndrome (PCOS), but being under, or over-weight, having a hormonal imbalance, or a mild thyroid condition, can also result in a long cycle [1].

Managing irregular or long menstrual cycles;

Note: Occasionally you might skip a period, or notice a delay in its arrival, making your cycle longer than 35 days- this is usually caused by stress. However, you should consult a doctor if your period remains absent for over 6 months (assuming pregnancy and the menopause have been ruled out).

This section is for those for whom it is ‘normal’ to have regular, or irregular, cycles over 35 days in length.

TOP TIP! Make sure you keep track of your cycle, in a diary, symptom tracker chart, or smartphone application. This will help your doctor to make a more informed diagnosis.

The most common cause of a long or irregular cycle is Polycystic Ovary Syndrome (PCOS), please see our dedicated page for more information on this condition.

Once PCOS, hormonal medication, and thyroid conditions have all been ruled out, the likely cause of a long or irregular cycle is Functional Hypothalamic Amenorrhea – a lack of ovulation/period caused by hormonal imbalance; stress; being over, or under-weight, or over-exercising [1].

Managing Functional Hypothalamic Amenorrhea:

NoteIf the hypothalamus (part of the brain) senses stress or malnutrition (i.e. over, or under-eating or exercising), it perceives a ‘threat’ and so temporarily shuts down reproductive processes until the threat has passed [2]. This is why this issue is called ‘Functional Hypothalamic Amneorrhea’ (FHA).  There are three types of FHA: weight loss-related, stress-related, and exercise-related amenorrhea.

The good news is that it responds particularly well to the four steps outlined on our ‘all symptoms‘ page;

A hormone-balancing diet– Excessive or sudden weight loss can cause your periods to stop. Severely restricting the amount of calories you eat stops the production of hormones needed for ovulation [2]. If you are trying to reduce weight, do not restrict your diet so much that your periods stop, just try a healthy hormone-balancing diet, as described in our blog, and increase the amount of exercise that you take.

Your GP may refer you to a dietitian if you’re underweight (a body mass index (BMI) of less than 18.5). The dietitian will be able to advise you about how to regain weight safely. If your weight loss is caused by an eating disorder, such as anorexia, you may be referred to a psychiatrist.

Likewise, if you’re overweight, your body may produce an excess amount of oestrogen, which can also cause your periods to stop [3]. Your doctor may refer you to a dietitian if you’re overweight or obese (a BMI of 30 or more), and it’s affecting your periods.

– Try nutritional supplements– If you are underweight, and lacking periods, you are at high risk of developing osteoporosis in later life [2]. Getting enough calcium and vitamin D is essential to building strong, dense bones when you’re young and to keeping them strong and healthy as you age [4].  Take supplements if you are not sure that you are getting enough calcium (RDA: 1000mg), or Vitamin D (RDA: 400-800 IU), through diet alone. Find out more about this topic on the National Osteoporosis Society website.

– Other useful supplements for treating FHA are Magnesium (100-300 mg daily) which can help to regulate your hypothalamus and pituitary gland function [5], and Vitex Agnus Castus (200-500 mg of extract daily) to promote ovulation by preventing your pituitary gland from making too much prolactin (which can prevent ovulation) [6].

TOP TIP! If you eat a lot of soy, try reducing how much you consume for a few weeks to see if that regulates your cycle… Soy can inhibit the release of follicle-stimulating hormone (FSH) (which triggers ovulation) produced by your hypothalamus [5].

Avoid excessive exercise – The stress that intense physical activity places on your body can affect the hormones responsible for your periods. Losing too much body fat through intense exercise can also stop you ovulating [2]. You are advised to reduce your level of activity if excessive exercise has caused your periods to stop.

If you’re a professional athlete, you may benefit from seeing a doctor who specialises in sports medicine. They’ll be able to give you advice about how to maintain your performance whilst looking after your health. As with those who are underweight, athletes who have stopped having periods are at high risk of developing osteoporosis in later life [2]. Bone loss can also lead to decreased athletic performance, decreased ability to exercise or train at desired levels of intensity or duration, and increased risk of injury [7].

Healthy exerciseRegular exercise can boost mood, improve self-esteem, and help reduce weight, or maintain a healthy weight [8]. So, if your periods have stopped due to being overweight, exercise is a great way to help get them started again [9].

Self-esteem– Improving your self-esteem is very important in regard to reducing stress, managing weight issues, eating healthily, and taking a healthy amount of exercise.

The Oxford Cognitive Therapy Centre produces highly effective (and cheap!) booklets on ‘Building Self-Esteem‘ and ‘Overcoming Eating Disorders‘ (the focus is on bulimia, anorexia and binge eating, rather than obesity- although research shows that these conditions share several characteristics and risk factors [10]- especially in regard to low self-esteem). Individuals might also benefit from the support of a specialist counsellor.

Reduce stress hormones– In the case of stress-induced FHA, it is precisely the high levels of stress hormones (especially cortisol) in the body that trigger the hypothalamus to shut down reproductive processes [11].

If you’re not sure what’s causing your stress, track stressful episodes in a diary (or on your symptom tracker chart!). Then review it to identify the possible triggers…

Regular exercise, such as running, swimming or yoga, can help you relax, as can breathing exercises. The NHS also recommends these ‘10 stress busters‘…

If you have tried the suggested tips and tricks for at least 3 months, and your symptoms do not improve, please consult your doctor.

If you have any suggestions, or tips, for managing irregular or long cycles- please let us know– we can share them with others!

Further information:

Page last reviewed and updated: June 2018


  1. NHS (2016) Irregular Periods. [ONLINE] Available at: [Accessed 30 March 2017].
  2. Meczekalski, B., Katulski, K., Czyzyk, A., Podfigurna-Stopa, A., & Maciejewska-Jeske, M. (2014) ‘Functional hypothalamic amenorrhea and its influence on women’s health’ Journal of Endocrinological Investigation, 37(11), 1049–1056.
  3. Seif MW, Diamond K, Nickkho-Amiry M. (2015) ‘Obesity and menstrual disorders’. Best Pract Res Clin Obstet Gynaecol. May;29(4):516-27. doi: 10.1016/j.bpobgyn.2014.10.010. Epub 2014 Nov 1. Review. PubMed PMID: 25467426.
  4. National Osteoporosis Society (2016) Healthy eating for strong bones. [ONLINE] Available at: [Accessed 30 March 2017].
  5. Briden, L. (2015) Period Repair Manual; Natural Treatment for Better Hormones and Better Periods Amazon pp. 156
  6. van Die MD, Burger HG, Teede HJ, Bone KM.(2013) ‘Vitex agnus-castus extracts for female reproductive disorders: a systematic review of clinical trials’. Planta Med. May;79(7):562-75. doi: 10.1055/s-0032-1327831. Epub 2012 Nov 7. Review. PubMed PMID: 23136064.
  7. Berz K, McCambridge T. (2016) ‘Amenorrhea in the Female Athlete: What to Do and When to Worry’ Pediatr Ann. Mar;45(3):e97-e102. doi: 10.3928/00904481-20160210-03. PubMed PMID: 27031318.
  8. NHS. (2011) Physical Activity Factsheet. [ONLINE] Available at: [Accessed 22 March 2017].
  9. Orio F, Muscogiuri G, Ascione A, Marciano F, Volpe A, La Sala G, Savastano S, Colao A, Palomba S. (2013) Effects of physical exercise on the female reproductive system. Minerva Endocrinol. Sep;38(3):305-19. Review. PubMed PMID: 24126551.
  10. Day J, Ternouth A, Collier DA. (2009) ‘Eating disorders and obesity: two sides of the same coin?’ Epidemiol Psichiatr Soc. Apr-Jun;18(2):96-100. PubMed PMID: 19526739.
  11. Berga SL, Daniels TL, Giles DE. (1997) ‘Women with functional hypothalamic amenorrhea but not other forms of anovulation display amplified cortisol concentrations’. Fertil Steril.  Jun;67(6):1024-30. PubMed PMID: 9176439.