A late period is most commonly caused by pregnancy, but dozens of other factors can delay your cycle, from stress and weight changes to hormonal conditions like thyroid disorders or polycystic ovary syndrome. A normal menstrual cycle ranges from 21 to 34 days in adults, so a period that arrives a few days “late” may simply reflect your body’s natural variation. If your cycle length shifts by seven days or more from what’s typical for you, something worth investigating is likely going on.
What Counts as a Late Period
Your cycle length is measured from the first day of one period to the first day of the next. For most adults, that window falls between 21 and 34 days. A period that shows up a day or two later than expected is well within normal range, especially if you don’t track your cycle precisely. Cycles can also shift slightly from month to month without any underlying problem.
When a period is more than a week later than usual, that’s worth paying attention to. If you go 90 days or more without a period (and you’ve had regular cycles before), medical guidelines consider that secondary amenorrhea, a condition that warrants evaluation. For people with cycles that have always been irregular, the threshold is six months.
Pregnancy Is the First Thing to Rule Out
Even if you don’t think you could be pregnant, a home pregnancy test is the fastest way to narrow down the cause. Modern tests can detect the pregnancy hormone hCG as early as four days before your expected period, though accuracy improves significantly if you wait until the day your period is due. At that point, a test that can detect 25 mIU/mL of hCG (which most over-the-counter tests can) reaches about 99% accuracy.
If the test is negative but your period still hasn’t arrived after another week, test again. Early pregnancy produces very low hormone levels that can be missed on the first try, particularly if you tested before your period was actually late.
Stress and Your Cycle
Stress is one of the most common non-pregnancy reasons for a late period, and the mechanism is straightforward. When your body is under sustained psychological stress, it ramps up production of cortisol and other stress hormones. Those hormones activate a signaling pathway in the brain that directly suppresses the reproductive hormone cascade needed for ovulation. Specifically, stress hormones increase the activity of neurons that inhibit the release of gonadotropin-releasing hormone, the master switch for your cycle. No ovulation means no period, or at least a delayed one.
This isn’t limited to extreme trauma. A high-pressure stretch at work, a move, a breakup, or even chronic sleep deprivation can be enough to delay ovulation by days or weeks. Once the stressor eases, cycles typically resume on their own.
Low Energy Availability
Your body needs a minimum amount of energy to sustain a menstrual cycle. When you’re not eating enough to match your activity level, whether through intentional dieting, disordered eating, or heavy training without adequate fuel, the brain receives signals that energy is scarce. One key signal is a drop in leptin, a hormone produced by fat cells. Low leptin tells the hypothalamus to shut down reproductive hormone production, suppressing the hormones needed for ovulation and lowering estrogen and progesterone.
This condition, called functional hypothalamic amenorrhea, is especially common among athletes, dancers, and anyone going through rapid weight loss. It’s not just about being underweight. You can have a normal BMI and still be in an energy deficit if your calorie intake doesn’t match your output. Restoring adequate nutrition is the primary way to bring cycles back, though recovery can take weeks to months.
Significant weight gain can also disrupt cycles, partly because excess fat tissue produces extra estrogen, which can interfere with the normal hormonal rhythm that triggers ovulation.
Polycystic Ovary Syndrome
PCOS is one of the five most common non-pregnancy causes of missed periods. It’s a hormonal condition characterized by elevated levels of androgens (often called “male hormones,” though everyone produces them). The hallmark signs are irregular or absent periods, excess hair growth on the face or body, acne, and sometimes difficulty conceiving.
Diagnosis requires at least two of three features: irregular cycles, signs of elevated androgens (excess hair growth alone is considered a strong predictor), and a specific pattern on ovarian ultrasound showing 20 or more follicles in at least one ovary. A blood test measuring anti-Müllerian hormone can now be used as an alternative to ultrasound in adults. PCOS is manageable with lifestyle changes and, when needed, medication to regulate cycles or address specific symptoms.
Thyroid Problems
Your thyroid gland controls your metabolic rate, but it also has a direct effect on your reproductive system. An underactive thyroid (hypothyroidism) alters the secretion of hormones needed for normal ovarian function, reducing your chances of ovulating in any given cycle. Even subclinical hypothyroidism, where thyroid levels are only slightly off, can be enough to cause irregular periods.
An overactive thyroid can also disrupt cycle timing. Thyroid screening is a standard part of any workup for missed periods, and the fix is often as simple as thyroid medication to bring hormone levels back into range.
Hormonal Birth Control
If you use hormonal contraception, a missing period may be a built-in side effect rather than a sign of a problem. Hormonal IUDs that release levonorgestrel thin the uterine lining over time, and about 20% of users experience at least one 90-day stretch without a period during the first year. That rate starts low (under 1% in the first three months) and climbs steadily as the body adjusts.
Coming off hormonal birth control can also delay your period. After stopping the pill, patch, or ring, it can take one to three months for your natural cycle to re-establish itself. If your period hasn’t returned within three months of stopping contraception, that’s a reasonable point to check in with a healthcare provider.
Perimenopause
If you’re in your 40s (or sometimes your late 30s), a late period could be an early sign of the transition toward menopause. Perimenopause begins when ovulation becomes less predictable, which makes cycle length fluctuate. In early perimenopause, cycles start varying by seven or more days from their usual pattern. In late perimenopause, gaps of 60 days or more between periods are common.
This transition typically lasts several years and comes with other recognizable symptoms: hot flashes, sleep disruption, mood changes, and vaginal dryness. Perimenopause is a normal biological process, not a disorder, but tracking your cycles can help you and your doctor understand where you are in the transition.
Other Medical Causes
A few less common conditions can also stop or delay periods. Hyperprolactinemia occurs when the pituitary gland produces too much prolactin, the same hormone responsible for breast milk production. High prolactin suppresses the reproductive hormones that trigger ovulation. This can be caused by a small, usually benign pituitary growth called a prolactinoma, or by certain medications (some antipsychotics and anti-nausea drugs are common culprits).
Primary ovarian insufficiency, sometimes called premature ovarian failure, is a condition where the ovaries stop functioning normally before age 40. It affects roughly 1 in 100 women and leads to irregular or absent periods along with symptoms similar to menopause. Intrauterine adhesions, scar tissue inside the uterus from a prior surgery or infection, can also prevent normal menstrual bleeding even when hormones are functioning normally.
When a Late Period Needs Attention
A single period that’s a few days late, with a negative pregnancy test, is rarely cause for concern. But certain patterns signal that something more is going on. If you’ve had regular cycles and go three months without a period, guidelines recommend getting evaluated. The same applies if you’ve always had irregular cycles and go six months without one. Sudden changes accompanied by severe pelvic pain, new hair growth on your face or chest, milky nipple discharge, or hot flashes before age 40 are all worth bringing up sooner rather than later.
The initial workup is typically simple: a pregnancy test, blood work to check thyroid function and hormone levels, and sometimes an ultrasound. In most cases, the cause is identifiable and treatable.