Can your period make you feel sick? The period flu, explained
Yes. Many people feel flu-like just before or during their period: nausea, achiness, headaches, chills, tiredness and loose stools. This so-called period flu isn't an infection. It's mostly caused by prostaglandins, the chemicals that make the uterus contract, plus the drop in estrogen and progesterone. A real fever of 38°C (100.4°F) or more isn't part of it.
What period flu feels like
Period flu isn't a medical diagnosis, but it's a useful name for a very common cluster of symptoms that arrive with your period and leave a few days later:
- Nausea, sometimes vomiting
- Achy muscles, back and legs
- Headache
- Feeling cold, shivery or clammy
- Tiredness and heaviness
- Diarrhea or loose stools
- Dizziness or feeling faint
- Low mood or feeling fragile
Why your period can make you feel ill
| Cause | What it does |
|---|---|
| Prostaglandins | Make the uterus contract, but also act on the gut (nausea, diarrhea), blood vessels (dizziness) and pain nerves (aches, headache) |
| Falling estrogen and progesterone | Can trigger headaches and affect mood, sleep and energy |
| Inflammation | Inflammatory markers seem to rise around the period in some people, which may add to the achy, unwell feeling |
| Blood loss | Heavy periods can lower iron, leaving you tired and dizzy |
| Poor sleep | Cramps and night sweats break up sleep, which makes everything feel worse |
Researchers haven't studied period flu as a single thing, but the prostaglandin link is well established for cramps and the gut and dizziness symptoms that come with them. See nausea before your period, period diarrhea and dizzy on your period.
What helps
- Anti-inflammatory pain relief like ibuprofen or naproxen lowers prostaglandins, so it can ease nausea, aches and cramps together. Start it early; ask a pharmacist if it's right for you.
- Heat on your belly or lower back.
- Small, plain meals and sips of water, ginger tea or electrolyte drinks if you feel queasy.
- Rest and an early night on your worst day.
- Iron-rich foods if your periods are heavy. Ask a doctor about a blood test if you're often exhausted.
- Hormonal contraception can reduce symptoms for some people by thinning the lining.
Period flu usually follows the same schedule every month. Knowing which days are likely to be rough lets you plan a quieter day, before you're already feeling awful.
Feeling sick and feeling low
When your body feels unwell, your mood often follows: you may feel weepy, withdrawn or short-tempered. That's a normal response, not a character flaw. Our page on mood during your period explains why the first days of bleeding feel the way they do.
You have a fever of 38°C (100.4°F) or higher, a rash that looks like sunburn, vomiting with dizziness or confusion, especially while using a tampon or cup: these can be signs of toxic shock syndrome and need urgent care. Also see a doctor if you vomit every period, can't keep fluids down, faint, or symptoms keep you off school or work.
Frequently asked questions
Can your period give you a fever?
Feeling warm or chilly is common, but a true fever of 38°C (100.4°F) or more isn't caused by your period. See a doctor if you have one.
Why do I feel sick before my period starts?
Prostaglandins start rising a day or so before bleeding, and hormones are falling, which can bring nausea early. See can PMS cause nausea.
Can your period weaken your immune system?
Immune activity does shift across the cycle, but a period doesn't make you meaningfully more likely to catch a real flu.
How long does period flu last?
Usually 1 to 3 days, often starting just before bleeding and easing after the heaviest days.
Sources
- ACOG: Dysmenorrhea: Painful Periods FAQ
- Cleveland Clinic: Dysmenorrhea
- NHS: Period pain
- MedlinePlus: Painful menstrual periods
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
Nausea before your period: why you feel sick and what helpsNausea before your period is common. Why prostaglandins and hormone shifts make you feel sick, how to tell it from early pregnancy, and what settles it.Can PMS cause nausea?Can PMS cause nausea? Yes: prostaglandins, hormone shifts, cramps and headaches can all make you queasy before your period. What helps and when to test.
Why do I feel dizzy on my period?Dizzy on your period? Blood loss, low iron, cramps, prostaglandins and dehydration can make you lightheaded. What helps, and when to see a doctor.Mood swings during your period: what's normal and what helpsMood swings during your period: why many people feel relief while others stay low or tired, how pain and sleep shape mood, and when to see a doctor.
PMS symptom diary: what to track for your doctorHow to keep a PMS symptom diary doctors can use: the daily items, the 1 to 6 rating scale, how long to track, and how to read the chart before your visit.