Day 23 of the menstrual cycle
In short: what happens on day 23?
Day 23 of the menstrual cycle is when, if no pregnancy has occurred, the corpus luteum starts to shrink and premenstrual syndrome (PMS) symptoms may appear. Progesterone and oestrogen slowly begin to fall. This hormonal shift can affect your mood, sleep and appetite in the days leading up to your period.
Day 23 of the menstrual cycle – animated explainer
Day 23: 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
14 mm
Corpus luteum
21 mm
FSH
18
LH
18
Oestrogen
54
Basal body temperature
36.75°C
What is happening in your body today?
The uterine lining is at its thickest. Progesterone production by the corpus luteum starts to decrease.
Hormones
Progesterone and oestrogen start to fall.
How you might feel
You may notice irritability, tension, bloating, breast pain, headaches and sugar cravings.
Chance of pregnancy
The chance of pregnancy is very low.
Tips for today
- Regular exercise reduces PMS symptoms
- Limit caffeine, alcohol and salt
- Eat foods rich in calcium and vitamin B6
When to see a doctor
See your doctor if mood changes seriously affect your daily life and relationships (this may be PMDD).
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 do PMS symptoms start?
They usually start 5–10 days before your period – roughly days 18–25 of a 28-day cycle – and ease once your period begins.
How can you tell PMS from early pregnancy symptoms?
The symptoms can be very similar. The most reliable way to tell is to take a pregnancy test once your period is late.
What is PMDD?
Premenstrual dysphoric disorder is a severe form of PMS that significantly affects daily life and needs treatment.
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