Why is my period late? Looking beyond pregnancy for answers

Causes of late or missed periods

If your period is late and you’re sexually active, the possibility of being pregnant might pop into your mind first. While it is one possible cause of a delayed period, there are actually a number of other reasons that your period could be late or even not come at all. Our menstrual cycles are driven by certain hormones, particularly estrogen and progesterone, and anything that changes the natural fluctuation of these hormones can disrupt the regularity of your cycle. If you’re asking yourself, “why is my period late”, here are some of the more common causes:

1.Going through puberty or perimenopause

Age has a clear impact on our cycles. There are two main stages in our lives when our periods are often irregular – when we first start menstruating during puberty and when we begin the transition to menopause (when our periods stop completely). This transition is called perimenopause. During perimenopause, it’s common for periods to become irregular as our body’s estrogen levels fluctuate and ovulation becomes more unpredictable. [1,2,3] 

2. High stress levels 

Stress can affect your menstrual cycle by delaying or even stopping your period. This is because excess stress levels affect the hormones that regulate your cycle. Research has shown that feeling like you are under a lot of stress are linked to irregular menstrual cycles [4].

3. Pregnancy

If you’re sexually active and you know your period is late, it’s possible that you are pregnant. Taking a pregnancy test is the best way to detect a pregnancy. While manufacturers’ instructions vary from test to test, it’s generally recommended to take a pregnancy test the day after your period should have started. 

4. Weight and weight changes

Having a high body mass index, or BMI, can also impact your menstrual cycle. Scientists suspect that lower levels of certain proteins in your body and higher levels of testosterone for those with high BMI disrupts regular menstruation [4]. At the same time, any rapid or extreme weight loss brought on by changes in diet or exercise routines, or by an eating disorder, can also affect regular menstruation and cause late or missed periods [3,5].

5. Starting, stopping, or changing birth control

Starting, switching, or stopping certain hormonal birth control methods can cause changes to your cycle, including irregular cycles, for a period of time. In particular, studies have shown that women who stop taking oral contraception (like the pill) are more likely to experience longer and/or more variable cycles [6]. Birth control can also affect our periods. For example, hormonal birth control (pills, injections, implants, and IUDs) can cause irregular periods that can be lighter, while non-hormonal IUDs can cause heavier or prolonged menstrual bleeding [3].

6. Thyroid conditions

Your thyroid produces a certain hormone called thyroxine, and when it doesn’t produce enough, it’s known as hypothyroidism. When it produces too much, it’s known as hyperthyroidism. Both hypo- and hyperthyroidism can cause menstrual cycle disruptions – hyperthyroidism may be associated with longer cycle-lengths while those with hypothyroidism are more likely to experience heavy periods [7]. Hypothyroidism is usually managed with medication, while hyperthyroidism treatments include medicine, radioiodine, and surgery [8,9]. 

7. Polyendocrine metabolic ovarian syndrome (PMOS)

Formerly called polycystic ovary syndrome (PCOS), PMOS is a common hormone condition that impacts periods, fertility, mood, and hair growth. PMOS and its symptoms can range from mild to severe, but having irregular periods or long gaps between periods is one of the most common symptoms. [3,10] Talk to your doctor about next steps if you suspect you may have PMOS.

8. Other chronic conditions (and their treatments)

Some other long-term conditions, as well as their medical treatments, can affect the hormones that regulate your period. Diabetes [11] and celiac disease [12] are both linked to irregular periods. Pelvic inflammatory disease, a type of infection and inflammation of uterus, fallopian tubes, and/or ovaries can also cause abnormal vaginal bleeding [13] At the same time, some medications that are used to treat psychological disorders, depression, and acid reflux can cause irregular menstruation because they increase the amount of prolactin in the blood [14]. If you have any of these conditions or notice changes to your cycle after beginning any new medications, it’s important to speak with your doctor. 

9. Primary ovarian insufficiency (POI)

When our ovaries stop functioning normally before the age of 40, it's generally referred to as primary ovarian insufficiency, or POI. POI is not the same as perimenopause, which is your body’s transition into menopause (when periods stop completely), but a separate diagnosis that is estimated to affect about 1 in 100 women. While scientists are unsure exactly what causes POI, around 15% of cases are linked to a familiar occurrence (a close female relative had it), while a genetic cause can be identified in around 10% of cases. Up to 30% of women with POI also have an autoimmune disease. Irregular menstruation is a common symptom of POI because ovulation doesn’t regularly happen each cycle. [15] 

Delayed period vs. early pregnancy symptoms 

Both your menstrual cycle and pregnancy naturally involve changes to your hormone levels, and this can cause an overlap between early pregnancy symptoms and premenstrual syndrome (PMS) symptoms. If you're trying to figure out “why is my period late”, the similarities between these symptoms can make understanding what is going on in your body confusing. Here are the ones that early pregnancy and our periods have in common:

• Cramping: pain just before and during your period is caused by the uterus tightening as it prepares to shed its lining. In some cases, it can also be linked to other conditions like endometriosis [16]. In early pregnancy, on the other hand, cramping and period-like pain are most likely caused by hormonal changes and by your expanding uterus [17]. If you have any unexplained or severe abdominal pain or pain that doesn’t fade and/or gets worse, it’s important to contact your doctor.
• Breast Changes: sore breasts, or mastalgia, during your menstrual cycle and early in pregnancy are both linked to hormonal shifts [18,19]. 
• Fatigue: tiredness before your period and early in pregnancy is also linked to hormone changes [19,20]. Fatigue can also be linked to other factors, such as stress, an oncoming cold, lack of sleep, or an imbalanced diet [21].
• Headaches: menstrual-related headaches (MRH) are commonly caused by falling estrogen levels during your cycle [22]. Headaches early in pregnancy, on the other hand, are caused by a combination of hormone changes and increased blood flow and volume as your body begins to grow a new life [19].
• Appetite Changes: before and during your period and early on in pregnancy, new or different food cravings or aversions are common. Interestingly, researchers are still unsure what causes these changes. [19,23]

There is one symptom that is pretty unique to early pregnancy, and that is changes to your nipples. While breast pain or tenderness can be a symptom of early pregnancy or PMS, darkening of the skin around your nipples (called the areola) is a symptom related to pregnancy and not your menstrual cycle [19]. 

If your period is late, the best way to check if you’re pregnant is to take a pregnancy test. If a pregnancy test result is positive, it’s important to see a doctor right away. 

Treatment for missed or late periods

If you missed your period, confirming you are not pregnant can be the first step to take if you are sexually active. You can test for pregnancy at home with a simple urine test. It’s important to follow the guidelines to make sure your result is as accurate as possible. Keep in mind that while at-home tests can be up to 99% accurate, a negative test doesn’t always mean you aren’t pregnant – it might mean there isn’t enough pregnancy hormone present to register yet. You might need to test again, or consult with a doctor to completely rule out pregnancy.

If you know that you aren’t pregnant, there are steps you can take to try and naturally balance your hormones. Eating a balanced diet [24], getting enough sleep [25], and trying to manage your stress [4] are all important for overall health and wellbeing and may encourage a more regular cycle. Natural Cycles can also help you get to know your body better by making it easier to detect any changes to your body’s natural patterns.

If you’re struggling with irregular periods or experiencing changes in your cycle, it’s important to consult a doctor or healthcare professional. They may recommend adjustments to your lifestyle or prescribe medication or other treatments. In some cases, there are no treatments needed [26]. 

Treatment advice can generally depend on the severity of the issue and whether you are looking to become pregnant. A few of the most common treatment options include oral contraception, or changing contraception, cyclic progestin, or other nonsteroidal anti-inflammatory medications (NSAIDs), and counseling or nutritional therapy for eating disorders [27]. If you are thinking about coming off hormonal birth control, Natural Cycles can be a solution to help track your cycle and provide certified contraception. NC° powered by your biomarker data, helping you learn more about what is happening in your body while identifying your fertile and non-fertile days.

When to see a doctor

While the occasional irregular or missed period is usually nothing to be concerned about, if your periods are chronically irregular, you miss multiple periods, or you are experiencing any other changes to your normal cycle pattern, it’s important to speak with your doctor to help diagnose the underlying cause [26]. If you have taken a pregnancy test at least a day after you expected your period and/or 21 days from when you last had unprotected sex [28] and it's negative, but you still haven’t gotten your period and are concerned, contact your doctor.

If you can, try to keep a record of the changes to your cycle, including the length, a description of your menstrual bleeding (how much, how long), and any other symptoms you’re experiencing. If you use Natural Cycles, you can download your Cycle Report to share with your doctor, check your Cycle History to see how cycle lengths and symptoms compare, and be notified when any key cycle moments fall outside medical norms. 

Learn what’s going on in your body with Natural Cycles

If you’re interested in understanding what is going on in your body between periods, Natural Cycles can help — our Cycle Report feature shows an easy-to-read overview of your period dates, ovulation and more, making it quick and simple to share with your doctor. NC° is the first FDA-cleared birth control app, providing accurate information about your unique cycle using biomarkers from your own body. Pair it with a wearable like your NCº Band, Oura Ring, Garmin, or Whoop to seamlessly learn what’s happening with your cycle today.