Hypothyroidism & Periods: Heavy, Long & Irregular
An underactive thyroid (hypothyroidism) slows metabolism and disrupts the hormones that regulate ovulation, so periods often become heavier, longer, or more frequent, and can turn irregular. It usually comes with fatigue, cold sensitivity, weight gain, and dry skin. A simple blood test confirms it.
How hypothyroidism changes your cycle
Low thyroid hormone affects estrogen and progesterone balance and ovulation, which shows up in your bleeding pattern.
- Heavier or longer periods (menorrhagia) are common.
- Cycles can shorten and come more often, or turn irregular.
- Ovulation may be disrupted, affecting fertility.
- Alongside: fatigue, weight gain, cold, dry skin, and low mood.
Know what your body needs, every day
PhaseBloom turns your cycle into a day-by-day plan for how to eat, move, rest, and care for your skin, so you stop guessing and start working with your hormones.
Know what your body needs, every day
PhaseBloom turns your cycle into a day-by-day plan for how to eat, move, rest, and care for your skin, so you stop guessing and start working with your hormones.
Frequently asked questions
Can an underactive thyroid cause heavy periods?
Yes. Hypothyroidism is a common and often overlooked cause of heavy or prolonged periods. If your periods have become noticeably heavier along with fatigue or weight gain, ask your doctor for a thyroid test.
Will treating my thyroid fix my periods?
Often, yes. Once thyroid hormone levels are corrected with treatment, many women see their periods return to a more normal pattern over a few cycles.