Missing a period for one month is common and, in most cases, not a sign of anything serious. The average menstrual cycle runs about 29 to 30 days, but individual cycles can vary by five or more days in either direction. A single skipped period can result from stress, a change in weight, new medication, or simply a cycle where ovulation was delayed or didn’t happen. That said, if you miss three or more periods in a row, the American College of Obstetricians and Gynecologists recommends getting evaluated.
Rule Out Pregnancy First
If there’s any chance you could be pregnant, a home test is the fastest way to know. Most home pregnancy tests claim over 99% accuracy when taken from the day of your expected period. To hit that accuracy, a test needs to detect a hormone concentration of at least 25 mIU/mL, which is the level most people reach by the day their period is due. Testing too early, before that hormone has built up, can give a false negative. If your first test is negative but your period still hasn’t arrived a week later, test again.
Stress and Your Cycle
Stress is one of the most common reasons for a missed period outside of pregnancy. When your body produces excess cortisol, the stress hormone, it slows the brain signals that trigger ovulation. Specifically, cortisol lengthens the interval between pulses of luteinizing hormone, which is the chemical messenger your brain sends to tell your ovaries to release an egg. Without that signal arriving on schedule, ovulation gets delayed or skipped entirely, and your period follows suit.
This doesn’t require a major life crisis. A demanding month at work, poor sleep, travel across time zones, or an illness like the flu can be enough to delay ovulation by a week or two. Once the stressor passes, most people see their cycle return to its usual pattern within one to two months.
Weight Changes and Energy Balance
Your body needs a certain amount of stored energy to maintain a regular cycle. Research shows that mature women typically need around 26 to 28% body fat for consistent ovulatory cycles. Losing even 10 to 15% of your normal body weight can be enough to stop periods altogether, and severe weight loss (around 30% of ideal body weight) reliably causes amenorrhea.
This works in both directions. Rapid weight gain can also disrupt your cycle by altering hormone levels, particularly estrogen, which is partly produced in fat tissue. If you’ve recently started a restrictive diet, ramped up exercise significantly, or gained weight quickly, your missed period may be your body recalibrating. Restoring a stable energy balance usually brings periods back, though it can take several months.
Hormonal Birth Control
If you use hormonal contraception, a missing period may be a built-in feature rather than a problem. Hormonal IUDs cause periods to stop in about 50% of users by the one-year mark and 60% by two years. Injectable contraception leads to no periods in up to 71% of users after two years. Even combination birth control pills, when taken continuously, result in amenorrhea in 88% of users by 12 months.
Stopping birth control can also cause a gap. After discontinuing hormonal methods, it can take your body a few months to resume its own ovulation pattern. One missed period after going off the pill or removing an IUD is typical and not a cause for concern on its own.
PCOS and Irregular Ovulation
Polycystic ovary syndrome is one of the most common hormonal conditions in women of reproductive age, and irregular or missing periods are a hallmark symptom. PCOS is diagnosed when someone has at least two of three features: irregular or absent ovulation, elevated levels of androgens (hormones like testosterone), and a characteristic appearance of the ovaries on ultrasound.
With PCOS, the ovaries may contain many small follicles that never mature enough to release an egg. Without ovulation, the hormonal cascade that produces a period doesn’t complete. If your missed period is part of a longer pattern of unpredictable cycles, cycles that frequently run longer than 35 days, or cycles accompanied by acne, excess facial or body hair, or difficulty losing weight, PCOS is worth discussing with a healthcare provider. It’s manageable with treatment, and getting a diagnosis opens up options for regulating your cycle.
Thyroid Disorders
Your thyroid gland influences nearly every reproductive process from puberty through menopause. Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can cause missed periods, heavy periods, or cycles that come too frequently. Hypothyroidism is the more common culprit. It’s characterized by high levels of thyroid-stimulating hormone (TSH) paired with low levels of active thyroid hormones.
Other signs of a thyroid problem include unexplained fatigue, changes in weight, feeling unusually cold or hot, hair thinning, and constipation. A simple blood test can check your thyroid function, and if levels are off, treatment typically restores regular cycles.
Perimenopause
If you’re in your 40s or even your late 30s, a missed period could be an early sign of perimenopause. This transition phase typically starts in the mid-40s but can begin as early as the mid-30s, and it lasts eight to ten years before menopause. During perimenopause, cycles may grow longer or shorter, bleeding may become heavier or lighter, and you may start skipping periods altogether.
Other signals include hot flashes, night sweats, sleep disruption, and mood changes. A single missed period at 42 doesn’t mean menopause is imminent, but if the pattern continues or you notice other symptoms, it’s useful context for understanding what your body is doing.
When One Missed Period Becomes a Pattern
A single skipped period, with a negative pregnancy test and no other symptoms, is rarely something to worry about. The clinical threshold for secondary amenorrhea, the term for periods stopping in someone who previously had them, is three consecutive months without a period. That’s the point at which guidelines recommend investigation, because three months of absent cycles raises the likelihood that something specific, like a thyroid imbalance, PCOS, or significant hormonal disruption, is driving the problem.
Before that three-month mark, keep track of your cycle dates, any symptoms you notice, and any recent changes in your life: new medications, weight fluctuations, stress levels, sleep quality, or exercise habits. This information is genuinely helpful if you do end up needing a medical evaluation, and it often reveals the explanation on its own.