The Menstrual Phase: Hormones, Symptoms & What to Expect
The menstrual phase is the first stage of the menstrual cycle: it begins on day 1, the first day of bleeding, and typically lasts 3 to 7 days. It happens because estrogen and progesterone from the previous cycle have dropped to their lowest point, causing the built-up uterine lining to shed. On a reference 28-day cycle it covers roughly days 1–5, though the exact days depend on your own cycle length.
Hormones through the cycle
Estrogen: At its lowest point of the cycle, just starting to rise again.
Progesterone: At its lowest point, as last cycle's corpus luteum has broken down.
LH: Low and steady.
FSH: Beginning to rise, signaling the ovaries to start growing new follicles.
A simplified illustration of estrogen, progesterone, LH and FSH across a typical 28-day cycle. Individual levels and timing vary, and this is not a lab measurement.
Menstruation is triggered by a sharp drop in estrogen and progesterone at the end of the previous cycle. Without these hormones to maintain it, the uterine lining built up over the past month breaks down and is shed as menstrual blood.
At the same time, follicle-stimulating hormone (FSH) starts to rise, prompting a new group of follicles to begin developing in the ovaries. Clinically, this is already the start of the follicular phase, overlapping with the days you bleed.
Many people notice cramping in the first 1 to 3 days, caused by prostaglandins making the uterus contract to shed its lining, along with lower energy and a need for more rest. Symptoms and their intensity vary a lot from person to person and from cycle to cycle.
Cycle syncing: nutrition & movement
| Focus | Nutrition | Movement |
|---|---|---|
| Iron & minerals | Iron-rich foods (leafy greens, legumes, lean red meat) to help replace what is lost with bleeding. | Low-intensity movement: walking, stretching, restorative yoga. |
| Comfort & cramps | Magnesium-rich foods (nuts, seeds, dark chocolate) and warm fluids; some people find less caffeine helps. | Heat (a warm bath or heating pad) alongside gentle activity. |
| Energy | Regular, balanced meals rather than skipping food when appetite dips. | Rest when you need it. This is not the phase to chase a personal best. |
These are general, low-risk wellness suggestions, not medical treatment. Evidence for timing diet and exercise to cycle phase ("cycle syncing") is still limited.
Find your own dates
Enter your usual cycle to see roughly which days fall into each phase for you.
Your estimated phase dates this cycle
Menstrual Phase
1–5
Follicular Phase
6–11
Ovulatory Phase
12–15
Luteal Phase
16–28
Know exactly which day you’re on
Bloom Private's PhaseCalculator engine reads the dates you log and works out which phase you're in, entirely on your iPhone. No accounts, no servers, and nothing to sell: your cycle data stays on your iPhone unless you choose to export it or turn on Apple Health.
Frequently asked questions
Most periods last between 3 and 7 days. Bleeding that regularly lasts longer than 7 days, or is heavy enough to soak a pad or tampon every hour, is worth discussing with a doctor.
Cramps are caused by prostaglandins, hormone-like substances that make the uterus contract to shed its lining. Mild to moderate cramps are common; pain severe enough to disrupt daily life is not something to just live with.
They overlap. Clinically, menstruation is the start of the follicular phase: FSH is already rising and new follicles are developing while you bleed. This page treats them as separate stages because that's how most people find it useful to track their cycle.
Explore the other phases
Sources
This page is for general education, not medical advice, and Bloom Private is not a contraceptive method. Talk to a healthcare professional about your own cycle and symptoms.