Reviewed June 2019

Is it true that the mini pill causes no side effects?

Tough day at work: businesswoman having a splitting headache.

All prescribed drugs can have potential side effects and contraceptives are no different. Some side effects may be undesirable and some may be beneficial. Knowing all the potential side effects of different types of contraception can help you make a well-informed choice about which type is best for you.

What is the mini pill and how does it work?

The mini pill, also known as the progestogen only pill (POP), is an oral contraceptive pill which contains synthetic progestogens, and acts through various different mechanisms. It thickens the cervical mucus, making it difficult for sperm to go through the cervix and enter the uterus (womb). It also makes the endometrium (inner lining of the uterus) thinner, which should also make it difficult for a fertilised egg to implant.1 Newer pills containing third-generation progestogens, such as desogestrel, act principally by preventing the release of the egg from the ovary.

When compared with the combined oral contraceptive pill (COCP), the mini pill certainly has its benefits due to the fact that it does not contain oestrogen. Hence, it can be used in circumstances where oestrogen is contraindicated or should be used with caution, such as in breastfeeding women, older women, and women in whom there is a presence of cardiovascular risk factors.

How good is the mini pill at preventing pregnancy?

The mini pill contains a lower dose of progestogen than the COCP and its hormonal action on cervical mucus lasts only for about 24 hours.2 So it is very important to take the pill around the same time every day in order for it to be effective. The POP is more than 99% effective in preventing pregnancy in perfect use.3 That means if the drug is taken correctly for a year, less than one out of 100 women will get pregnant.

However in practical life, perfect use of a contraceptive method is not always achieved. Sometimes you forget to take the pill, or take it too late, and with that kind of use, described as ‘typical use’, it has an effectiveness of 90 – 97%. In cases of failed contraception, pregnancies of mini pill users are more likely to be ectopic (fertilised egg being implanted outside the womb), than those occurring in women who use other contraceptive methods that work by suppressing ovulation.4

This may be due to the fact that progestogen reduces the motility of fallopian tubes and thus slows the transport of fertilised egg towards the uterus. For this reason, women should seek medical advice in the presence of warning symptoms such as lower abdominal pain, heavy vaginal bleeding, missed periods, or pain during sexual intercourse.

Does it cause bleeding between periods?

Irregular vaginal bleeding while on the mini pill is common but does not indicate a health risk most of the time. In fact, almost half of mini pill users experience prolonged bleeding and up to 70% get breakthrough bleeding or spotting.5 This is due to the fluctuation of hormone levels in the body with the use of mini pill. Progestogens are important in maintaining the stability of the endometrium. As the progestogens in the mini pill are short-acting, even a small delay of several hours in taking the pill may lead to a low blood concentration of progestogens, resulting in shedding of the endometrium and bleeding. This irregular bleeding varies depending on factors like the type, and the dose, of POP used, the duration taken, and concentration of oestrogen in the body.

Bleeding is more common among users of newer POPs containing desogestrel than in users of the traditional POPs, and the irregular bleeding often settles with time. Irregular bleeding is one of the most common reasons for discontinuation of use of the mini pill.6

Does the mini pill cause weight gain? Does it decrease libido?

These seem to be major concerns in women when deciding on a contraceptive method. Some say yes and some say no, while some even report weight loss or having increased libido while on the pill. Despite the different perceptions, there is only limited scientific evidence to support a causal association between weight change and POP use.7

However, this concern cannot be completely disregarded as different women react differently to the mini pill, and unfortunately no doctor can predict how it will affect you precisely. Genetic predisposition, diet, and lifestyle, as well as other medical conditions, may all play a role. Drug companies may promote their brands as non-weight gaining or even weight losing, but remember that there is no sound evidence to prove it. However, just because your friend gained weight while on the mini pill, it might not be the same for you. And the same goes with libido — there is simply not enough research done on the topic.

Mini pill and mood — are they related?

Depression associated with POP use is a topic of much debate at present. Mood changes have been reported in many women on the mini pill. Effects of progestogen on neurotransmitters in brain, such as glutamate and serotonin, which affects the mood, may be one possible reason. A Danish study has found that use of hormonal contraception, especially among adolescents, was associated with a first diagnosis of depression and that the risk is higher in those who use the mini pill than the COCP.8

Even though there is evidence for association of mini pill use and depression, no study has been able to conclude that the mini pill is the causative factor. However, the possibility exists, and it’s important to seek medical advice if you experience any unexplained changes of mood.

Are there any other common complaints associated with the mini pill?

While some COCPs are used in the treatment of acne, the mini pill is known to aggravate the condition in some users.9

Development of acne is influenced by hormones, and changes in the progesterone-to-oestrogen ratio may lead to acne. Unlike COCP, which regulates the hormonal levels in the body, the mini pill, containing only progestogens and not oestrogen, leads to excessive sebum production. Sebum is the oily secretion from sebaceous glands, which when secreted in excess causes clogging up of hair follicles, leading to development of acne.

Breast tenderness is another thing many mini pill users complain of. As progestogen causes enlargement of the breast glands leading to stretching of ligaments in the breast, it results in pain and tenderness. This may alleviate after several months of use. However, this is a common side effect of the COCP as well.

With the unpredictable action of progestogens on ovulation, the mini pill is also known to increase the risk of functional ovarian cysts. Although this might sound alarming, many cysts regress spontaneously with time.

Who should not use the mini pill at all?

POPs are best avoided in certain preexisting medical conditions, as set out by the UK Medical Eligibility Criteria for Contraceptive Use (UK MEC). Even though no evidence supports an association between mini pill use and breast cancer, if you currently have breast cancer then it is classed as an unacceptable health risk for POP use.10 Ischemic heart disease (also known as coronary artery disease), stroke, past breast cancer, severe cirrhosis, and liver tumours are listed as conditions where proven risks outweigh the benefits of using POP.11

Also, if you are already on drugs such as antiepileptics, antiretrovirals, or some antibiotics like rifampicin, which induce liver enzymes, the mini pill is not the contraceptive of choice for you. Liver enzymes metabolise (process and change the form of) progestogen in the body. When these enzymes are induced by the above drugs, the progestogen in the mini pill metabolises faster, resulting in a lower concentration of progestogen in the blood. When the required concentration of progestogen for contraception is not there, it increases the risk of contraception failure. For this reason, if you are on any drugs, it’s always best to inform your doctor and get their opinion before choosing a method of contraception.

Research has proven some side effects, debunked several myths, and some topics are yet to be researched in full. You will be able to discuss all your concerns with your doctor, who will be able to help you make the best choice regarding your method of contraception.

Last updated June 2019
Next update due 2021

Dr. Shehara Ariyaratne, MBBS

Shehara graduated from the University of Colombo, with degrees in Medicine and Surgery. She has research experience in various fields of medicine, having worked at the Epidemiology Unit of Sri Lanka and National Institute of Infectious Diseases. She is currently practising paediatrics and radiology at the Lady Ridgeway Hospital, Colombo, the main paediatric hospital in the country. Though a medical doctor in profession, writing has always been her passion and she hopes her articles will help empower women.

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  1. Cooper, D.B., et al., Oral Contraceptive Pills, StatPearls publishing, last updated May 15, 2019, [accessed online],, (accessed 30 June 2019)
  2. FSRH, Progestogen-only Pills, April 2019, [online],, (accessed 30 June 2019)
  3. Ibid.
  4. Ibid.
  5. Ibid.
  6. Ibid.
  7. Lopez, M., et al., ‘Progestin‐only contraceptives: effects on weight’, Cochrane Database of Systematic Reviews, Art. No: CD008815, 2016.
  8. Skovlund, W., et al., ‘Association of Hormonal Contraception With Depression’, JAMA Psychiatry, vol. 73, no. 11, 2016, pp. 1154-1162. Available from JAMANetwork, (accessed 21 March 2017).
  9. Słopień, R., et al., Use of oral contraceptives for management of acne vulgaris and hirsutism in women of reproductive and late reproductive age, Menopause Review, March 2018, vol 17, issue 1, pp 1-4
  10. Faculty of Sexual and Reproductive Healthcare (FSRH), UK Medical Eligibility Criteria For Contraceptive Use (UKMEC), 2016, [online],, (accessed 30 June 2019)
  11. Ibid

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