Picture this: your period is late. You take a pregnancy test, hoping this could (finally) be the month, and it comes up negative. You’re disappointed but also confused as to what could be going on with your body. Does this sound familiar?

If you’ve experienced this exact scenario, you are far from alone. Menstrual cycle irregularities occur in 14-25% of women of childbearing age. While a “normal” menstrual cycle ranges from 21 to 35 days, it’s not unusual for small variations to occur each month. However, if your period is consistently irregular, you should speak with your healthcare provider about a potential underlying cause — especially if you’re trying to conceive.

So, why is your period late if you’re not pregnant? Here are a few possibilities: 

woman taking a walk on a tree-lined path

8 Possible Reasons for Late Periods

1. Stress

Stress can have a significant impact on your cycle. When you're under a lot of stress, your body releases stress hormones like cortisol. These hormones can interfere with the hormones that regulate your menstrual cycle, leading to missed or irregular periods. Stress can also cause a condition called hypothalamic amenorrhea, which is when the hypothalamus (a part of the brain) stops signaling the body to ovulate.

Remember: everyone deals with stress differently, so it’s important to find healthy ways to cope — whether it be through exercise, relaxation techniques, or counseling — especially if you’re battling infertility.

2. Changes in body weight

Low body weight, especially in cases of anorexia or bulimia, may cause irregular or absent periods. Extreme exercise or a big change in your exercise routine, such as training for a marathon, can have the same effect.

On the other hand, a higher-than-average BMI can cause your body to produce too much estrogen (also called estrogen dominance), which may alter the menstrual cycle. If you are struggling with any of the above, it’s important to speak with your healthcare provider who can help come up with the best course of action to help manage your weight and regular your cycle.

3. Birth control

It’s very common to experience a change in your menstrual cycle when you stop taking birth control or start a new type of contraceptive. Remember: birth control is often prescribed to help regulate the menstrual cycle or reduce uncomfortable period symptoms, so it’s important to note that it can often take your body up to three months to regulate after stopping, starting, or changing birth control methods.

If your menstrual cycle hasn’t normalized after 3 months of discontinuing hormonal birth control, be sure to consult with your doctor.

birth control package

4. Chronic diseases

There are several chronic conditions that may alter your menstrual cycle including PCOS, Diabetes, Cushing Syndrome (when the body makes too much cortisol), Asherman’s Syndrome (scar tissue in the uterus), Endometriosis, and even Celiac Disease. 

For example, PCOS is a hormonal disorder that affects the ovaries and the production of hormones like estrogen and progesterone. It is characterized by the presence of small cysts on the ovaries, as well as high levels of androgens (male sex hormones) in the body. These hormonal imbalances can disrupt the menstrual cycle and prevent ovulation from occurring. Ovulation is necessary for the menstrual cycle to be regular, so this often results in irregular or absent periods. 

Even if you have had regular menstrual cycles in the past, many of these conditions can present themselves later in life, or even after giving birth, leading to hormonal changes. The best way to get to the bottom of this is to discuss it in detail with your doctor, who can give you a clear diagnosis and treatment plan for moving forward.  

5. Thyroid issues

Thyroid problems can affect the menstrual cycle in a number of ways. The thyroid is a gland located in the neck that produces hormones that regulate metabolism and energy levels. When the thyroid is not functioning properly, it can disrupt the production of other hormones in the body, including those that regulate the menstrual cycle.

If you have an overactive thyroid (hyperthyroidism), you may experience irregular periods or no periods at all. This is because high levels of thyroid hormone can interfere with the menstrual cycle and prevent ovulation from occurring. Alternatively, if you have an underactive thyroid (hypothyroidism), you may experience heavy or prolonged periods. This is because low levels of thyroid hormone can cause an imbalance in the levels of estrogen and progesterone, leading to changes in the menstrual cycle.

Thankfully, thyroid conditions can typically be well-managed with medication, so if you are experiencing irregular periods or other menstrual changes and have — or suspect you have — a thyroid condition, it’s a good idea to ask your doctor for a simple blood draw to check your thyroid levels to determine next steps.

6. Illness

If you're sick with a fever or an infection, such as COVID, it can throw off your menstrual cycle.

7. Medications

Certain medications, such as antidepressants or antipsychotics, can interfere with your menstrual cycle.

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8. Pregnancy

Although pregnancy is likely not the cause of your missed or late period, in this case, it's important to rule it out. If you're sexually active and your period is late, it's always a good idea to take a pregnancy test to be sure (yes, even if you’re experiencing infertility!). 

There are many possible reasons why your period could be late even if you’re not pregnant — from stress and weight changes to hormone imbalances and certain medications. It's important to remember that everyone’s body is different, and what may be normal for one person may not be normal for another. It's always a good idea to pay attention to your symptoms and speak with a healthcare provider if you're concerned about any changes to your menstrual cycle. Most often, your doctor can help recommend lifestyle swaps or medication that can help keep your cycles regular so you aren’t left guessing when your period will arrive. And if you’re trying to conceive, rest assured that there are options available to you as well. You’ve got this! 

Whitney Welsh is a writer and content creator who is passionate about telling stories that inspire change. She has 12+ years of marketing and communication experience at industry-leading brands including Southwest Airlines, Hilton, and Baylor Scott & White Health. In her personal life, Whitney is inspired by travel, spending time outdoors, and volunteering in her community. She is currently expecting her first baby with her husband (and their dog, Odin).