Period Flu: Why You Feel Sick Before Your Period and What to Do About It
- Apr 6
- 7 min read
Every month, like clockwork, it happens.
A few days before your period arrives you start to feel run down. Body aches you cannot explain. A heaviness and fatigue that sleep doesn't touch. Maybe a headache, hayfever, some nausea, digestive upset.
You feel, in a word, terrible.
And then your period starts and within a day or two you feel almost normal again. If this sounds familiar, there is a name for what you are experiencing. It is informally called period flu. And while it is not a medical diagnosis in the traditional sense, it is a real physiological phenomenon with a clear mechanism behind it. More importantly, it is not something you
simply have to accept every month.
Period flu is not imaginary and it is not inevitable. Understanding what is driving it is the first step toward doing something about it.
What is Period Flu?
Period flu refers to a cluster of flu-like symptoms that appear in the days before menstruation and typically resolve once bleeding begins. Unlike the actual influenza virus, period flu is not infectious and not caused by a pathogen. It is caused by the body's own inflammatory chemistry. The symptoms can include body aches and joint pain, fatigue and low energy, headaches, nausea, digestive upset including diarrhoea, chills and temperature sensitivity, brain fog, and a general feeling of being unwell. The timing is the tell. It appears premenstrually and lifts when the period arrives.
Dysmenorrhoea, or painful menstruation driven by prostaglandin activity, affects between 45% and 95% of women who menstruate, with prevalence highest in women under 25. A 2022 review published in PMC found that primary dysmenorrhoea is characterised by painful cramps and systemic symptoms in the absence of any identifiable pelvic pathology, and that increased prostaglandin synthesis in the endometrium is the central mechanism. The broader systemic symptoms of period flu occur through the same pathway (Itani et al., PMC, 2022).
The Prostaglandin Connection
To understand period flu, you need to understand prostaglandins. These are hormone-like signalling molecules produced throughout the body, including in the lining of the uterus, the endometrium. They play a role in inflammation, pain signalling, and the contraction of smooth muscle.
In the days before your period, progesterone levels drop sharply as the corpus luteum breaks down. This drop triggers the release of enzymes that set off the prostaglandin production cascade. The prostaglandins cause the uterus to contract, which is what helps it shed its lining. This is normal and necessary.
The problem arises when prostaglandin production is excessive. High levels of prostaglandins, particularly prostaglandin F2 alpha and prostaglandin E2, do not stay contained to the uterus. They enter the bloodstream and circulate through the body. And this is where the flu-like picture comes from.
Circulating prostaglandins can cause smooth muscle contractions throughout the gastrointestinal tract, which is why nausea, cramping, and diarrhoea are common. They can lower the pain threshold systemically, which explains the body aches and joint pain. They can affect thermoregulation, producing the chills and temperature sensitivity. They drive a broader inflammatory response that produces fatigue and general malaise. The fact that these symptoms lift when bleeding begins is not coincidental. Prostaglandin levels are highest in the first one to two days of menstruation and fall as the period progresses. As they drop, so do the symptoms.
Why Does it Happen to Some Women More Than Others?
Not every woman experiences period flu, and those who do experience it with varying severity. This is not random. The degree to which prostaglandins are produced and how well the body processes them is influenced by several factors that vary between individuals.
Oestrogen dominance, a state where oestrogen is high relative to progesterone, is one of the most significant drivers. Oestrogen amplifies prostaglandin production. When progesterone is relatively low and oestrogen relatively elevated, the prostaglandin cascade at the start of menstruation is more pronounced.
Dietary factors also play a role. Prostaglandins are synthesised from arachidonic acid, which comes primarily from animal fats. A diet high in pro-inflammatory omega-6 fatty acids and low in anti-inflammatory omega-3 fatty acids tips the balance toward greater prostaglandin production. Conversely, omega-3 fatty acids compete with arachidonic acid in the prostaglandin pathway and favour the production of less inflammatory prostaglandin types.
Nutritional deficiencies, particularly in magnesium and zinc, affect prostaglandin metabolism. Magnesium helps regulate prostaglandin activity and smooth muscle contractility. Low magnesium is consistently associated with more severe menstrual symptoms.
Underlying conditions including endometriosis, adenomyosis, and fibroids are associated with higher prostaglandin production and more severe systemic symptoms. If your period flu is severe and accompanied by very heavy or very painful periods, it is worth investigating whether an underlying condition is contributing.
Chronic inflammation and a high overall inflammatory load in the body also exacerbate the picture. The more inflamed the system, the more amplified the prostaglandin response at menstruation.
"Period flu sits at the intersection of hormonal balance, nutritional status, and systemic inflammation. When I am working with a woman who experiences significant premenstrual flu-like symptoms, I am not just looking at her cycle in isolation. I am looking at her overall inflammatory load, her oestrogen and progesterone balance, her nutritional status, and her gut health, because all of these influence how her body handles the prostaglandin surge at the start of each cycle. The good news is that addressing these things makes a significant difference." - Gemma Knaap, Naturopath (BHSc Naturopathy, Certified Natural Fertility Educator, Gut Microbiome Analyst) | Southernwood Apothecary & Clinic | Albany, WA | Telehealth across Australia
What Can You Do About It?
Period flu is not something you simply have to manage through each month. Addressing the drivers, rather than just the symptoms, tends to produce significant improvement over a few cycles.
• Support hormonal balance, particularly progesterone relative to oestrogen. This involves looking at oestrogen metabolism and clearance, stress levels (chronic stress suppresses progesterone), liver and gut health, and in some cases targeted herbal or nutritional support.
• Reduce dietary inflammation. Increasing omega-3 fatty acids from sources like oily fish, flaxseed, and walnuts directly influences the prostaglandin pathway. Reducing processed foods, refined vegetable oils high in omega-6, and excess animal fats reduces the substrate available for pro-inflammatory prostaglandin production.
• Address nutritional deficiencies. Magnesium, zinc, vitamin D, and B vitamins all play roles in prostaglandin metabolism, smooth muscle function, and hormonal balance. Deficiencies in these are common in women with significant menstrual symptoms.
• Support gut health. The gut plays a central role in oestrogen clearance, and poor gut health contributes to oestrogen dominance. A healthy gut microbiome, particularly the estrobolome, supports balanced oestrogen levels and can reduce the hormonal drivers of excessive prostaglandin production.
• Investigate underlying conditions. If symptoms are severe, it is worth ruling out endometriosis, adenomyosis, fibroids, or other conditions that may be amplifying the prostaglandin picture.
This is Not Just Part of Being a Woman
One of the things that frustrates me most in clinical practice is how often significant menstrual symptoms are dismissed. Women are told that pain and feeling unwell each month is normal, that it is just part of having a period, that there is nothing to be done beyond taking pain relief and pushing through. Period flu is common. That does not make it normal. It is a signal that the inflammatory and hormonal picture needs attention. And when that attention is given, properly and thoroughly, most women see real improvement.
You do not have to reorganise your life around your menstrual cycle every month. Telehealth consultations available across Australia.
Frequently Asked Questions
What causes period flu?
Period flu is caused by elevated prostaglandin levels in the days before and at the start of menstruation. Prostaglandins are inflammatory signalling molecules produced by the uterine lining that trigger the contractions needed to shed the endometrium. When prostaglandin production is high, these molecules enter the bloodstream and cause systemic effects including body aches, nausea, fatigue, headaches, and digestive symptoms. The severity varies between women depending on hormonal balance, nutritional status, dietary factors, and whether an underlying condition is present.
Why do my period flu symptoms go away when my period starts?
Prostaglandin levels are highest immediately before and in the first one to two days of menstruation, then decline as the period progresses. This is why the systemic symptoms of period flu typically peak in the day or two before bleeding begins and resolve within the first day or two of the period itself. The improvement is not coincidental. It directly follows the falling prostaglandin curve.
Is period flu the same as PMS?
Not exactly. PMS, or premenstrual syndrome, is a broader category of premenstrual symptoms that includes mood changes, bloating, breast tenderness, and irritability, among others. Period flu refers more specifically to the flu-like physical symptoms, aches, chills, fatigue, nausea, that are driven primarily by prostaglandin activity. There is overlap, and many women experience both, but the mechanisms are not identical. PMS involves a broader hormonal picture including progesterone withdrawal and serotonin fluctuations, while period flu is more specifically prostaglandin-mediated.
Can diet affect period flu symptoms?
Yes, meaningfully. Prostaglandins are synthesised from arachidonic acid, which comes primarily from animal fats in the diet. A high intake of pro-inflammatory omega-6 fatty acids, combined with low intake of anti-inflammatory omega-3 fatty acids, shifts the prostaglandin balance toward more pro-inflammatory types. Increasing omega-3 intake from oily fish, flaxseed, and walnuts, while reducing processed food and refined vegetable oils, directly influences the prostaglandin pathway and can reduce the severity of symptoms over several cycles.
Could period flu be a sign of something more serious?
Severe period flu, particularly when accompanied by very heavy or very painful periods, can be a sign of an underlying condition such as endometriosis, adenomyosis, or fibroids, all of which are associated with higher prostaglandin production and more pronounced systemic symptoms. If your symptoms are significantly affecting your quality of life, investigation is warranted rather than simply managing through it each month.
Can a naturopath help with period flu?
Yes. A naturopath can help identify and address the hormonal, nutritional, and inflammatory drivers of excessive prostaglandin production. This typically involves looking at oestrogen and progesterone balance, dietary factors, nutritional deficiencies, gut health, and overall inflammatory load. The goal is to reduce the severity of symptoms at the source rather than managing them once they arrive. This work complements medical investigation and care where underlying conditions are suspected.
References
Itani, R. et al. (2022). Primary dysmenorrhea: Pathophysiology, diagnosis, and treatment updates. Korean Journal of Family Medicine / PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC8943241/
Nagy, H. et al. (2023). Dysmenorrhea. StatPearls, NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK560834/
Wieser, F. et al. (2007). Inflammatory Markers in Dysmenorrhea and Therapeutic Options. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC7068519/
American College of Obstetricians and Gynecologists (ACOG). (2024). Dysmenorrhea: Painful Periods. https://www.acog.org/womens-health/faqs/dysmenorrhea-painful-periods
Marjoribanks, J. et al. (2022). Review: Primary dysmenorrhoea and the role of prostaglandins. PMC. Cited in: Medical News Today, October 2024.
Tags: period flu, painful periods, prostaglandins, hormonal health, naturopath, women's health, PMS, period pain, menstrual health, telehealth, Albany WA
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