Feeling unusually tired or fatigued during menstruation, often called “period fatigue,” is common and can impact daily activities. This article explores the biological reasons behind this sensation.
Hormonal Shifts
The menstrual cycle involves significant fluctuations in estrogen and progesterone, directly affecting energy levels. In the luteal phase before menstruation, estrogen levels peak then rapidly decline, while progesterone rises. This estrogen drop can contribute to sluggishness and tiredness.
As the period begins, both estrogen and progesterone are at their lowest. This hormonal environment can prevent effective melatonin release, making it harder to fall and stay asleep. Serotonin, a neurotransmitter influencing mood and energy, often declines with decreasing estrogen, further lowering energy and changing mood.
Iron Deficiency
Menstrual blood loss can deplete iron stores, potentially leading to iron deficiency or anemia. Iron is a component of hemoglobin, which transports oxygen throughout the body in red blood cells. Low iron levels mean the body cannot produce enough hemoglobin, reducing oxygen delivery to tissues and organs.
Insufficient oxygen supply can result in extreme tiredness, weakness, and fatigue. Women with heavy menstrual bleeding are at increased risk of iron deficiency anemia due to significant iron loss each period. Fatigue is often more severe in individuals with heavy menstrual bleeding than those with lighter flows.
Sleep Disruptions
Menstrual symptoms and discomfort can directly interfere with quality sleep. Cramps, bloating, headaches, and breast tenderness can make it difficult to fall or stay asleep, or achieve restorative sleep. A person’s body temperature also increases slightly before their period, contributing to poor sleep.
Disrupted sleep patterns directly lead to daytime exhaustion and tiredness. Studies indicate that women may experience more disturbed sleep, including less rapid eye movement (REM) sleep, in the days before their period. This lack of restorative sleep accumulates, worsening fatigue.
Inflammation and Pain
The body’s inflammatory response during menstruation can also contribute to fatigue. During this time, the uterus produces prostaglandins, hormone-like substances that cause uterine muscles to contract to shed the uterine lining. While necessary for menstruation, high levels of prostaglandins can lead to intense cramps and systemic inflammation.
The body expends energy dealing with pain and inflammation, leading to a general feeling of being unwell and exhausted. Prostaglandins also influence pain levels and can cause increased pain sensitivity. The presence of chronic inflammation and the energy demand of managing pain can drain the body, resulting in significant fatigue that is distinct from fatigue caused by sleep disturbances or iron deficiency.