Feeling cold, chilly, or experiencing shivers just before or during menstruation is a common experience. This phenomenon is a normal physiological reaction related to the complex hormonal and chemical fluctuations that characterize the monthly menstrual cycle. The feeling of being cold arises from several distinct biological processes, including the rapid change in internal body temperature set-point, a possible reduction in the body’s heat-generating capacity, and a temporary systemic inflammatory response. Understanding these underlying mechanisms offers a clear explanation for why the body can feel unexpectedly cold.
Hormonal Shifts Affecting Body Temperature
The primary explanation for the cold sensation is found in the fluctuation of the reproductive hormones, estrogen and progesterone, which directly influence the body’s internal thermostat, the hypothalamus. Progesterone is a thermogenic, or heat-producing, hormone that acts on the hypothalamus to raise the basal body temperature (BBT) during the second half of the menstrual cycle. This phase, known as the luteal phase, follows ovulation and is characterized by elevated progesterone levels.
The body maintains this slightly higher temperature for roughly two weeks. If conception does not occur, the corpus luteum, which produces progesterone, begins to break down, leading to a sharp drop in progesterone levels immediately preceding the period. This rapid decline effectively resets the body’s internal thermostat to the lower set-point of the follicular phase. The body perceives this sudden drop from a higher temperature to a lower one as a sensation of coldness or chills. Estrogen, dominant during the first half of the cycle, can also promote heat loss, further contributing to the feeling of being cold when progesterone levels fall.
Anemia and Reduced Heat Production
Another factor contributing to a persistent feeling of coldness, particularly for those with heavy bleeding, is the potential for iron deficiency anemia. Menstrual bleeding, especially heavy menstrual bleeding (menorrhagia), can lead to a significant loss of iron over time. Iron is needed to produce hemoglobin, the protein in red blood cells responsible for transporting oxygen from the lungs to all tissues and organs.
When the body’s iron stores are depleted, resulting in iron deficiency anemia, the amount of oxygen delivered to tissues is reduced. This lack of oxygen delivery can impair the metabolic rate of cells, which are responsible for generating internal body heat. With a reduced metabolic capacity, the body struggles to generate and maintain sufficient warmth, leading to symptoms like weakness, fatigue, and a heightened sensitivity to cold. Women who consistently experience heavy periods are at a greater risk for this form of anemia, which can make the cold sensation a more chronic issue.
Prostaglandins and Systemic Inflammation
Beyond hormonal shifts and iron status, the release of inflammatory mediators known as prostaglandins plays a role in generating flu-like symptoms, including chills. When the uterine lining is shed at the start of the period, the body releases prostaglandins to induce the necessary uterine muscle contractions that expel the tissue.
These compounds act as chemical messengers and can sometimes enter the bloodstream and travel systemically. Prostaglandins are involved in the body’s inflammatory response, and when they act outside of the uterus, they can cause symptoms similar to a low-grade infection. This systemic action can include muscle aches, headaches, and the feeling of chills or shivering, which is the body’s attempt to warm itself up. The binding of prostaglandins with receptors in the hypothalamus, the area that regulates body temperature, may also directly contribute to these temperature-related discomforts.
Practical Strategies and Medical Indicators
For many, managing the cold sensation involves simple self-care measures that help regulate the body’s temperature. Layering clothing, using a heating pad on the abdomen, or consuming warm beverages can provide direct comfort and counteract the feeling of chilliness. Maintaining a diet rich in iron, or speaking with a healthcare provider about iron supplementation if bleeding is heavy, can help support the body’s capacity for heat production.
While feeling cold is often a normal part of the menstrual cycle, it is important to recognize indicators that suggest a more serious underlying issue. A person should consult a doctor if the coldness is accompanied by a true fever, severe fatigue, lightheadedness, or dizziness. Unusually heavy bleeding, defined as needing to change a pad or tampon every hour for several consecutive hours or passing clots larger than a quarter, should also prompt a medical consultation, as these are signs of potential severe iron deficiency anemia that requires treatment.