A missed period has many possible explanations, and pregnancy is only one of them. Stress, hormonal shifts, changes in weight or exercise, contraception, and several medical conditions can all delay or stop your period. If you previously had regular cycles and have now gone three months without a period, or six months if your cycles were already irregular, that’s the clinical threshold where evaluation is recommended.
Rule Out Pregnancy First
The most straightforward step is a home pregnancy test. Most kits are 98% to 99% accurate when used as directed, and the best time to take one is after you’ve already missed your expected period. Testing earlier can produce a false negative because the pregnancy hormone your body produces may not yet be high enough to detect. If you get a negative result but your period still hasn’t arrived after another week or two, test again or see a provider for a blood test, which picks up lower levels of the hormone sooner.
Stress and Your Cycle
Your brain is the starting point for your entire menstrual cycle. A region in the brain sends a hormonal signal that eventually tells your ovaries to release an egg. When you’re under significant stress, your body produces more cortisol, and cortisol directly interferes with that signal. It reduces both the frequency and strength of the pulses your brain sends to trigger ovulation. No ovulation means no period.
This doesn’t require a catastrophic life event. Prolonged work pressure, sleep deprivation, grief, anxiety, or a major life change like moving or starting school can all produce enough cortisol to disrupt your cycle. The effect is usually temporary. Once the stressor resolves or you find better ways to manage it, cycles typically resume on their own within a few months.
Not Eating Enough for Your Activity Level
Your body needs a minimum amount of energy to support reproduction. When the calories you take in don’t cover what you burn, your brain treats fertility as non-essential and dials down the same hormonal signals that stress disrupts. Research on female athletes has identified a specific threshold: when energy availability drops below about 30 calories per kilogram of lean body mass per day, periods often stop.
You don’t have to be a competitive athlete for this to happen. Restrictive dieting, rapid weight loss, or simply increasing exercise without eating more can all push you below that threshold. It can also occur at any body size. If your period disappeared around the same time you changed your eating or exercise habits, that connection is worth paying attention to. Restoring adequate nutrition is the primary way to bring your cycle back, though it can take several months.
Hormonal Contraception
Some forms of birth control are designed to thin the uterine lining so much that there’s very little to shed each month, and for many users, periods stop entirely. This is a known and expected effect, not a sign that something is wrong.
Among people using the hormonal implant, about 22% stop getting periods altogether, while another 34% experience only infrequent spotting. Hormonal IUDs have a similar effect, with the likelihood of lighter or absent periods increasing the longer the device is in place. Continuous use of birth control pills (skipping the placebo week) will also eliminate monthly bleeding. If you recently started, stopped, or switched contraception, give your body a few cycles to adjust. After stopping hormonal birth control, it can take one to three months for regular ovulation to resume.
Polycystic Ovary Syndrome (PCOS)
PCOS affects 10 to 13% of women of reproductive age, making it one of the most common reasons for irregular or missing periods. In PCOS, the ovaries produce higher than normal levels of androgens (often called “male hormones,” though all bodies make them). This hormonal imbalance can prevent eggs from maturing and being released on schedule, so you may go weeks or months between periods.
Other signs that point toward PCOS include acne that persists past your teens, excess hair growth on the face or body, thinning hair on the scalp, and difficulty losing weight. Not everyone with PCOS has all of these symptoms. A provider can check your hormone levels and do an ultrasound to look for the characteristic pattern of small follicles on the ovaries. Treatment focuses on managing symptoms and restoring regular cycles, often through lifestyle changes, hormonal contraception, or medications that help your body respond to insulin more effectively.
Thyroid Problems
Your thyroid gland sets the pace for many of your body’s processes, including your menstrual cycle. When the thyroid is underactive (hypothyroidism), your body compensates by increasing production of a brain hormone that, as a side effect, stimulates prolactin. Prolactin is the same hormone responsible for milk production after pregnancy, and elevated levels suppress the hormonal cascade that triggers ovulation. The result is missed or very irregular periods.
An overactive thyroid (hyperthyroidism) can also disrupt your cycle, though the mechanism is different. Common clues for thyroid issues include unexplained fatigue, weight changes, feeling unusually cold or hot, hair thinning, and changes in mood or energy. A simple blood test can check thyroid function, and treatment to normalize thyroid levels usually restores regular periods.
High Prolactin Levels
Even without a thyroid problem, prolactin can rise on its own and interfere with your cycle. Certain medications, particularly some antipsychotics, anti-nausea drugs, and antidepressants, are a common cause. In rarer cases, a small benign growth on the pituitary gland (called a prolactinoma) overproduces prolactin. About 9% of women being evaluated for absent periods turn out to have elevated prolactin. A hallmark symptom is unexpected milky nipple discharge when you’re not pregnant or breastfeeding, though not everyone with high prolactin experiences this. A blood test can measure your levels, and the condition is very treatable.
Perimenopause
If you’re in your 40s and your periods have become unpredictable, perimenopause is a likely explanation. This transitional phase before menopause typically begins in the mid-40s, though some women notice changes as early as their mid-30s. As your ovaries gradually produce less estrogen, ovulation becomes inconsistent. You might have a 25-day cycle one month and a 40-day cycle the next, or skip a period entirely.
A useful rule of thumb: if the length of your cycle consistently varies by seven or more days from what’s normal for you, you may be in early perimenopause. If you’re going 60 days or more between periods, you’re likely in late perimenopause. This phase can last anywhere from a few years to a decade before periods stop completely. Hot flashes, sleep changes, mood shifts, and vaginal dryness are other common signs that the transition is underway.
When a Missed Period Needs Attention
A single late period, especially during a stressful month, is rarely cause for concern. But certain patterns suggest it’s time to see a provider: three or more consecutive missed periods when you’re not pregnant or on contraception, sudden changes in cycle regularity that persist, or missed periods accompanied by new symptoms like vision changes, persistent headaches, unusual hair growth, or nipple discharge. A typical workup involves blood tests to check hormone levels, thyroid function, and prolactin, sometimes followed by an ultrasound. Most causes of a missing period are manageable once identified.