Spotting between periods: causes and when to get tested

In everyday language, spotting is a small amount of blood that does not need a pad or tampon, only a panty liner, or that leaves a mark on underwear. Bleeding is a larger amount of blood that needs sanitary protection. In the medical literature, however, what matters is less the amount than the timing: bleeding outside the expected window of menstruation is called intermenstrual bleeding, and bleeding during contraceptive use outside the planned break is described as unscheduled bleeding or spotting.

The international federation FIGO has developed two complementary systems for abnormal uterine bleeding in the reproductive years: a system of terminology for symptoms and a system for classifying causes, known by the acronym PALM-COEIN. The first part (polyp, adenomyosis, leiomyoma, malignancy and hyperplasia) describes structural causes, the second (coagulopathy, ovulatory dysfunction, endometrial, iatrogenic, not yet classified) non-structural ones. In practice this means that the same complaint, spotting, can have very different origins, so the work-up should be organised rather than based on a single test.

This study is valuable because it is based on the general population rather than on women who reach hospital clinics, where the proportion of organic findings is always higher. It shows that spotting is widespread and often transient. It has limitations, however: it concerns only perimenopausal women (40-54 years), relies on self-report in questionnaires, and lasted two years, so rare, late-diagnosed cancers could have gone undetected. It therefore cannot be used to conclude that spotting can always be ignored; what follows is that spotting alone is not proof of disease, and age, risk factors, recurrence and accompanying symptoms should decide the next steps.

The most innocent cause of mid-cycle spotting is ovulation. Before the egg is released, the estradiol level rises and peaks, and around ovulation it falls before progesterone starts to climb. The lining of the uterus (endometrium), which is sensitive to these swings, may briefly lose its hormonal support and give a small, short-lived bleed. Such spotting is usually pale, pinkish or brownish, lasts a day or two, and appears at roughly the same cycle day that corresponds to ovulation. It may be accompanied by egg-white-type mucus and one-sided ovulation pain, which we discuss separately in the article on ovulation pain.

This mechanism fits the physiology of the cycle well, but the hormonal explanation is mechanistic and rests mainly on textbook knowledge rather than on large studies that measured ovulatory spotting and hormone levels at the same time. It is therefore best to treat ovulatory spotting as a diagnosis of exclusion, not as the default explanation of every mid-cycle spotting. If the spotting is heavy, lasts longer than two or three days, is linked to pain or recurs on different days of the cycle, it is unlikely to be ovulation alone.

In women using hormonal contraception, spotting is one of the most common side effects, especially in the first months. It occurs with pills (particularly low-oestrogen pills, progestogen-only pills and missed pills), implants, depot medroxyprogesterone injections, patches and rings, and levonorgestrel-releasing intrauterine devices. The mechanism is that constant progestogen action changes the structure of the endometrium: it becomes thin, fragile and rich in delicate vessels that bleed easily and unpredictably.

A 2025 review of treatment of unscheduled bleeding on hormonal contraception notes that it is a common reason for stopping the method, and that good counselling before starting improves satisfaction. For persistent bleeding, non-steroidal anti-inflammatory drugs and oestrogen (alone or with a progestogen in pills) are most often used, and small studies suggest a possible effect of doxycycline, mifepristone, tranexamic acid and other substances. The authors state explicitly, however, that the evidence is limited. Changing the method or dose should therefore be discussed with a doctor and not done on your own.

Beyond ovulation and contraception the list of causes is long, so a doctor starts with questions about age, cycle regularity, medicines, sexual activity and recent cervical screening. The list below organises the commonest mechanisms; the order does not reflect how often each occurs in a given person.

Bleeding disorders (for example von Willebrand disease) are more often associated with heavy periods but can also appear as irregular bleeding. Thyroid disease, both underactive and overactive, disturbs ovulatory cycles and can cause spotting, which is why TSH is among the basic tests for irregular bleeding. In perimenopause spotting is common, but this is exactly the age at which the work-up should be more careful, because it is the period in which the risk of endometrial changes rises.

Short answer: rarely, but it depends on age and on whether the woman still menstruates. In younger women, endometrial or cervical cancer is rare among the causes of this symptom, and hormonal causes, pregnancy and infection dominate. From about age 45 and in the presence of certain risk factors (obesity, long-standing lack of ovulation, tamoxifen use, diabetes, hypertension), assessing the endometrium becomes more important. Guidelines differ in their precise age thresholds and indications for taking a sample, so the decision is always made by a doctor after taking a history and performing an ultrasound.

These data illustrate well why a symptom alone is not enough for a diagnosis, yet still deserves attention. An odds ratio of 4.7 for intermenstrual bleeding means that among women with cervical cancer this symptom occurred several times more often than among controls, but because cervical cancer is rare, the absolute risk for an individual woman with spotting remains small. That is why recurrence of the symptom, cervical screening and examination of the cervix with a speculum matter.

The contrast between the two groups is the key point. Before menopause spotting is common, often resolves by itself, and the cancer risk in the population is low. After menopause bleeding is far less common, yet it accompanies about 91% of endometrial cancers, and about 9 in 100 women with such bleeding turn out to have cancer, which cannot be ruled out without testing. For this reason any bleeding after menopause (that is, at least 12 months after the last period), even a single and small one, requires a gynaecological consultation and usually an assessment of the endometrium by transvaginal ultrasound and, if necessary, a biopsy. Most causes turn out to be benign, such as atrophy of the lining, a polyp or hyperplasia without atypia, but only the work-up establishes this.

The standard approach follows one principle: first the things that are common and quick to exclude, then imaging, and invasive procedures last. Individual centres may use a slightly different order, but the general logic is similar in most recommendations on abnormal uterine bleeding.

It is worth stressing that ultrasound is a first-line test but does not replace taking a sample when suspicion is justified. In young women whose history, examination and ultrasound do not point to a structural cause, and whose symptom fits ovulation or a contraceptive effect, observation and keeping a bleeding diary are usually enough.

Such a diary is a valuable tool: it helps distinguish ovulatory spotting from premenstrual spotting, spot a link with taking pills and avoid unnecessary tests. It does not replace medical assessment if the symptoms recur.

Spotting between periods has two faces: in the reproductive years it is usually a signal from the cycle or from contraception, while after menopause it is one of the few symptoms that really must be explained. We recommend treating a first episode calmly but with the reflex of checking for pregnancy, and any recurring symptom with a diary and a visit to a gynaecologist. Large studies show clearly that a reliable risk assessment needs age, the pattern of the symptom and an examination, not just the word 'spotting'.