An irregular period is any change from what’s typical for your cycle. That could mean periods that come too frequently, too far apart, or that are unpredictable. It can also refer to bleeding that’s heavier than usual, lighter than expected, or accompanied by spotting between cycles. While many people think of a “normal” cycle as exactly 28 days, a healthy cycle can fall within a wider range. What matters most is whether your pattern has shifted.
Irregular periods are common, especially during certain stages of life. But when changes persist, they can point to something worth investigating.
What Causes Irregular Periods?
Periods become irregular when ovulation is disrupted or when the uterine lining builds up and sheds in an unusual way. The causes can range from everyday lifestyle factors to medical conditions that benefit from treatment.
Stress and Lifestyle Changes
Stress is one of the most common reasons for a late or missed period. When your body is under stress, it produces more cortisol, which can interfere with the hormones that trigger ovulation. Rapid weight changes, intense exercise, travel, and sleep disruption can have a similar effect. Your body prioritizes stability, and when it senses strain, it may temporarily pause reproductive signals.
Polycystic Ovary Syndrome (PCOS)
PCOS is one of the most frequently diagnosed causes of irregular periods. It involves hormone imbalances that make ovulation less predictable. Some women with PCOS skip periods entirely, while others experience very long cycles or spotting. PCOS can also show up alongside symptoms like acne, increased facial or body hair, thinning scalp hair, and difficulty managing weight. The pattern varies from person to person, but inconsistent ovulation over time is a hallmark.
Thyroid Disorders
Your thyroid plays a key role in regulating metabolism, energy, and reproductive hormones. When thyroid function is too low (hypothyroidism), periods may become heavier, longer, or more frequent. When it’s too high (hyperthyroidism), periods may become lighter or less frequent. Thyroid symptoms can also include fatigue, hair changes, unexplained weight shifts, and changes in heart rate. Because thyroid issues are treatable and can mimic other conditions, they are often part of the workup for irregular cycles.
