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“Period Flu” is the popular term for a collection of flu-like symptoms—including body aches, fatigue, headaches, and sometimes a low-grade fever—that occur just before or at the start of your periods (menstruation).
It is not a real, contagious illness like influenza (popularly known as flu). Instead, these feelings are a severe form of Premenstrual Syndrome (PMS) caused by normal hormonal shifts and the production of prostaglandins in your body.
What causes Period Flu?
The feeling of being “sick” or “unwell” is primarily due to two powerful chemicals:
- Hormones (Progesterone and Estrogen):
Your key female hormones (estrogen and progesterone) drop sharply right before your period begins. This rapid hormonal decline can affect your mood, energy levels, and how your body handles pain, leading to general malaise and fatigue. - Prostaglandins (The Period Pain Chemicals):
These powerful chemicals are released to make your uterus contract and shed its lining (which causes menstrual cramps). Since prostaglandins are the same chemicals that signal pain and inflammation throughout the body, a high release can cause the “flu-like” symptoms like:- Body Aches: Inflammation and pain signals spreading to the joints and muscles.
- Low-Grade Temperature/Chills: Prostaglandins signaling the brain’s temperature center to turn up the heat.
- Digestive Issues: Prostaglandins causing contractions in the bowel, leading to diarrhea or nausea.
- Intense fatigue and general feeling of sickness.
More Answer For You
Hit Up Our Period Pain Calculator
For real, how bad is your pain? Our interactive tool uses a 1-10 pain scale and a few quick questions to help you get the full picture. In just a few clicks, you’ll know if your pain is a chill or a major red flag.



