Period Flu: The Endometriosis Symptom Your Doctor’s Probably Never Heard Of

Around 2014 I found myself regularly coming down with classic flu symptoms. A raised temperature, sore throat, aching limbs, heavy fatigue and sore lymph nodes in my underarms and groin would wipe me out for one to two weeks at a time. These periods of illness would often fall when I had a lot going on so I put them down to stress, a poor immune system or the knock-on effects of my blood sugar condition, reactive hypoglycemia. Now and then I would have a milder month or even go a month or two without symptoms so the timing appeared random and a pattern never emerged in my mind.

Once I started working full-time I had to take two to four days off sick each month, waking up tearful at the prospect of calling in sick yet again and typically dragging myself back to the office before I felt better. When the number of absences I racked up prompted a meeting with HR, I could only answer their concerned questions with an embarrassed shrug. I ultimately decided to go freelance in 2019.

The root cause was something I hadn’t even considered: endometriosis.

Although at least one in nine people assigned female at birth in Australia are affected by endometriosis, it takes an average of seven years from the onset of symptoms to receive a diagnosis. Commonly recognised symptoms are chronic pelvic pain, painful periods, pain during or after sex, pain when using the toilet, fatigue and infertility. In reality, the list doesn’t end there. Other regularly occurring symptoms around the time of your period can result from the cyclical inflammation that endometriosis entails – these may include symptoms you (and your GP) might never connect to your uterus, as I discovered.

When the symptoms began interfering with studying for my master’s degree in January 2021, I contacted my GP for help. She referred me to an endocrinology consultant for suspected chronic fatigue. The consultant immediately ruled this out and referred me on to the immunology department for testing. But questions about the timing of my sickness spells got me thinking. The symptoms always arrived seven to 10 days before my period. Late-night googling led me to a breakthrough: a post on the HealthUnlocked endometriosis forum about 'period flu'. I felt I had my answer. But even when all the immunology tests came back negative, the consultant resisted the idea it could be endometriosis, assuring me that my symptoms just didn’t line up. (After all, so far there has been limited research into the connection between menstruation and flu-like symptoms.) As an experiment, we agreed I would take the combined pill back-to-back to skip my periods. As if by magic, the flu symptoms stopped arriving each month, although the fatigue persisted.

The final puzzle piece slotted into place when stabbing pain in my lower right side took me to the hospital with suspected appendicitis in October 2021. Appendicitis was ruled out and no concrete alternative cause was offered but I left the hospital certain it was endometriosis. Sure enough, the pelvic pain came back every month thereafter, like clockwork. This was enough to finally get me a referral to a gynaecology consultant but, after a painful seven-month wait for an appointment, even she was sceptical that a laparoscopy (the most common diagnostic method for endometriosis) would find anything. She begrudgingly referred me for surgery but, faced with skyrocketing waiting times, I joined growing numbers of people turning to private care. 

In December 2022, laparoscopic surgery finally established that I have stage 2 (or mild on the scale of severity) endometriosis. My surgeon, endometriosis specialist Dr Edmond Edi-Osagie, confirmed my suspicion that it was the cause of my flu-like symptoms. "Contrary to previous thinking that endometriosis was a local pelvic disease," he explained, "with evolving knowledge of the condition we now know that endometriosis is a systemic inflammatory condition with certain local tissue (mostly pelvic) manifestations. Endometriosis is also a hormonally driven condition, primarily by oestrogens released by the ovaries, hence the cyclical (menstrual) influence on its manifestations. As such, endometriosis typically causes cyclical symptoms in keeping with oestrogen fluctuations during the menstrual cycle, including focal cyclical pelvic pains and systemic symptoms of inflammation such as fatigue, flu-like symptoms, general malaise and body pains, and mood fluctuations."

Now recovered from surgery and with a new lease on life, I hope to get the word out to people with a uterus (as well as doctors) everywhere that recurring flu-like symptoms can be a sign of endometriosis. Making period flu a recognised symptom could change lives by shaving years off diagnosis wait times for others like me.