Evidence-informed health library
Understand your cycle
Explore 25 plain-language guides to periods, follicular and luteal phases, hormones, ovulation, fertility signs, symptoms, and changing cycles across life.
The menstrual cycle, explained
A practical guide to cycle days, changing hormones, bleeding, ovulation, and why a “normal” cycle is a range—not one perfect number.
Read guide →Cycle basics · 4 minWhat happens during the menstrual phase?
Why bleeding starts, what the uterus is shedding, and which changes are useful to log.
Read guide →Cycle basics · 5 minThe follicular phase: follicles, estrogen, and timing
How the first half of the ovarian cycle prepares an egg and why its length often drives cycle variation.
Read guide →Ovulation · 5 minOvulation: what actually happens
The hormone surge, egg release, fertile timing, and the difference between predicting and confirming ovulation.
Read guide →Cycle basics · 5 minThe luteal phase: progesterone after ovulation
What the corpus luteum does, how progesterone affects the uterus and temperature, and how the phase ends.
Read guide →Cycle basics · 7 minYour cycle hormones: FSH, LH, estrogen, and progesterone
A plain-language map of the four hormones most often discussed in cycle tracking.
Read guide →Ovulation · 5 minUnderstanding the fertile window
Why fertility spans several days, how apps estimate that window, and why uncertainty matters.
Read guide →Ovulation · 6 minHow ovulation calculations work—and where they fail
A transparent look at period predictions, averages, ranges, and why “cycle day 14” is not a universal ovulation date.
Read guide →Ovulation · 5 minCervical mucus across the cycle
How discharge may change near ovulation and what infections, medications, and semen can make harder to interpret.
Read guide →Ovulation · 6 minBasal body temperature tracking
How to take waking temperature consistently, recognize a pattern, and avoid reading too much into one measurement.
Read guide →Ovulation · 6 minLH tests and ovulation predictor kits
What a positive urine test means, when ovulation may follow, and why an LH surge is not a guarantee.
Read guide →Symptoms & care · 6 minIrregular cycles: patterns, causes, and tracking
What “irregular” can mean, common reasons timing changes, and which details help at a medical visit.
Read guide →Symptoms & care · 5 minPeriod cramps: common does not mean untreatable
Why cramps happen, what to log, and signs that pain needs a clinician’s attention.
Read guide →Symptoms & care · 6 minHeavy periods and abnormal bleeding
Practical signs of heavy bleeding, why it matters, and when to seek urgent versus routine care.
Read guide →Symptoms & care · 7 minPMS and PMDD: timing is part of the diagnosis
How premenstrual symptoms differ from PMDD and why daily tracking across cycles can clarify the pattern.
Read guide →Symptoms & care · 7 minPCOS and menstrual cycles
Why PCOS may affect ovulation and cycle timing, what tracking can reveal, and why diagnosis needs clinical evaluation.
Read guide →Symptoms & care · 7 minEndometriosis: symptoms beyond “bad cramps”
Common patterns, why symptom severity varies, and how a cycle diary can prepare you for care.
Read guide →Symptoms & care · 5 minA missed period: pregnancy and other possibilities
What a late prediction means, when to test for pregnancy, and why periods may stop for other reasons.
Read guide →Life stages · 5 minFirst periods and cycle tracking for teens
What can be expected in the first years after menarche and how to track without expecting instant regularity.
Read guide →Life stages · 6 minPeriods after pregnancy and while breastfeeding
Why cycle return varies, why ovulation can precede the first period, and which postpartum bleeding signs are urgent.
Read guide →Life stages · 6 minCycle changes during perimenopause
Why timing and flow can change in the menopause transition and why new bleeding patterns still deserve assessment.
Read guide →Ovulation · 6 minCycle tracking is not the same as contraception
The important difference between an app prediction, a fertility awareness-based method, and proven contraceptive options.
Read guide →Ovulation · 6 minTracking while trying to conceive
How cycle dates and ovulation signs can support timing without turning uncertainty into false precision.
Read guide →Cycle basics · 5 minCycle tracking and health-data privacy
Questions to ask about accounts, cloud sync, exports, deletion, device security, and advertising.
Read guide →Symptoms & care · 6 minWhen period or pelvic symptoms need medical care
A calm, practical guide to routine appointments, prompt advice, and emergency warning signs.
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