Day 28 of the menstrual cycle
In short: what happens on day 28?
Day 28 of the menstrual cycle is the last day of a 28-day cycle, and your period usually starts the next day. Without a pregnancy, hormones are at their lowest and the uterine lining is ready to shed. If your period is late and you have had unprotected sex, taking a pregnancy test is recommended.
Day 28 of the menstrual cycle – animated explainer
Day 28: cycle dial, uterus and ovaries, hormone levels (illustrative animation).
What the animation shows
- FSH
- Follicle-stimulating hormone: starts the growth of follicles in the ovary
- LH
- Luteinising hormone: its sudden surge triggers ovulation
- E2
- Oestrogen (oestradiol): thickens the lining of the uterus
- P4
- Progesterone: prepares the uterus for a possible pregnancy
- BBT
- Thermometer and dots below: basal body temperature
- RING
- Coloured ring: the 28-day cycle and its phases; the green arc marks the fertile days
- MM
- The measurement in the uterus shows lining thickness; in the ovary it shows follicle or corpus luteum size
Phase
Luteal phase
Chance of pregnancy
Very low
Uterine lining
12 mm
Corpus luteum
11 mm
FSH
40
LH
15
Oestrogen
14
Basal body temperature
36.4°C
What is happening in your body today?
Shedding of the uterine lining is about to begin. Follicles for the new cycle have already started to grow in the ovary.
Hormones
Oestrogen and progesterone are at their lowest point in the cycle; FSH is rising.
How you might feel
You may have cramps, back pain and tiredness. PMS symptoms fade quickly once your period starts.
Chance of pregnancy
The chance of pregnancy is very low.
Tips for today
- If your period is late, take a pregnancy test
- Record your cycle length and symptoms
- Start the new cycle well rested
When to see a doctor
See your doctor if your period is more than 7 days late and your test is negative, if you have not had a period for more than three months, or if your cycles are shorter than 21 days or longer than 35 days.
Menstrual cycle day by day: table
| Day | What happens | Fertile window |
|---|---|---|
| Day 1 | First Day of Your Period | — |
| Day 2 | Heaviest Bleeding Day | — |
| Day 3 | FSH Rises, Follicles Grow | — |
| Day 4 | Bleeding Eases, Oestrogen Rises | — |
| Day 5 | Last Day of Your Period | — |
| Day 6 | Follicular Phase Begins | — |
| Day 7 | Dominant Follicle Is Selected | — |
| Day 8 | Oestrogen Rises, Fertile Window Nears | Low |
| Day 9 | Fertile Window Begins | Moderate |
| Day 10 | Fertile Window, Higher Pregnancy Odds | Moderate |
| Day 11 | 3 Days Before Ovulation | High |
| Day 12 | Oestrogen Nears Its Peak | High |
| Day 13 | LH Surge: Ovulation Is Near | Highest |
| Day 14 | Ovulation Day | Highest |
| Day 15 | Luteal Phase Begins | Moderate |
| Day 16 | Progesterone Rises | Low |
| Day 17 | Luteal Phase and Increased Appetite | — |
| Day 18 | Breast Tenderness May Start | — |
| Day 19 | Implantation Window Opens | — |
| Day 20 | Implantation Bleeding Possible | — |
| Day 21 | Progesterone Peak (Day 21 Test) | — |
| Day 22 | Mid-Luteal Phase | — |
| Day 23 | PMS Symptoms May Start | — |
| Day 24 | Hormones Start to Fall | — |
| Day 25 | Late Luteal Phase and PMS | — |
| Day 26 | Progesterone Drop and Cramps | — |
| Day 27 | 1 Day Before Your Period | — |
| Day 28 | Last Day of Your Cycle | — |
Frequently asked questions
When should you take a test if your period is late?
You can take a home pregnancy test from the day your period is due. If it is negative and your period still does not come, repeat it 3–5 days later or have a blood test.
When should you worry about an irregular period?
It should be checked if your cycles are consistently shorter than 21 days or longer than 35 days, if periods last longer than 7 days, or if you bleed between periods.
When do you ovulate if your cycle is longer than 28 days?
Ovulation usually happens about 14 days before your next period. For example, in a 32-day cycle it is around day 18.
Gynaecology check-ups and follow-up at SoftCare Clinic
Book an appointment with our specialist doctors for irregular periods, painful periods or pregnancy planning.
The information on this page is general guidance based on a typical 28-day cycle and does not replace a medical examination. It should not be used as a method of contraception.
Medical content editor: Op. Dr. Şükrü Sanus