Estrogen is at its lowest point when your period starts, but it doesn’t stay there. Within the first few days of bleeding, estrogen begins a gradual climb that continues well after your period ends. So the short answer is yes, estrogen does increase during your period, though it starts from its lowest baseline of the entire cycle.
Where Estrogen Stands on Day 1
Your period marks the beginning of a new menstrual cycle. It arrives because estrogen and progesterone both dropped sharply at the end of the previous cycle, and without those hormones supporting the uterine lining, the lining sheds. At this point, estrogen is at rock bottom. During the early follicular phase (the first several days of your cycle, which overlap with your period), estrogen can be as low as 12.5 pg/mL.
That low point is temporary. The drop in estrogen and progesterone actually triggers your brain to release more of a signal called FSH (follicle-stimulating hormone). FSH does exactly what its name suggests: it tells your ovaries to start developing a new follicle, the fluid-filled sac that will eventually release an egg. As early as days 1 through 4, the recruitment of new follicles is already underway, even while you’re still bleeding.
How Estrogen Starts Climbing
As FSH stimulates the growing follicle, the cells surrounding it begin producing estrogen. Specifically, FSH triggers these cells to convert other hormones into estradiol, the most potent form of estrogen. Estrogen levels rise in parallel with the size of the developing follicle and the increasing number of cells producing it.
This means the rise is slow at first. During the days of your period (roughly days 1 through 5 or 7), estrogen is climbing but still relatively low. The more dramatic increase happens after your period ends, during the mid-follicular phase, eventually peaking just before ovulation. By that point, estrogen can reach up to 166 pg/mL or higher, more than ten times its early-cycle low.
Progesterone Stays Flat
One important contrast: while estrogen begins its slow rise during your period, progesterone stays essentially negligible throughout this phase. Progesterone only enters the picture after ovulation, when the ruptured follicle transforms into a structure that produces it. During your period and the days that follow, progesterone has little influence on how you feel. The hormonal story of your period is really about estrogen waking back up while progesterone stays quiet.
What Rising Estrogen Does to Your Body
Even though estrogen is still low during your period, its gradual increase sets several things in motion. The most immediate effect is on your uterine lining. As estrogen rises, it stimulates the endometrium to begin rebuilding. This transition, called the proliferative phase, starts overlapping with the tail end of your period. Your cervix also responds to increasing estrogen, changing its position and the consistency of cervical mucus in the days after bleeding stops.
The mood and energy shifts many people notice toward the end of their period are tied to this rising estrogen as well. Research shows that during low-estrogen phases of the cycle, women tend to have stronger negative mood responses to stress and less activity in brain areas involved in emotional regulation. As estrogen climbs, it supports what researchers describe as “top-down” regulation of emotions: the brain becomes better at managing stress responses, reappraising negative situations, and dampening activity in areas linked to negative feelings. This is why many people report feeling noticeably better in the days right after their period compared to the days just before it.
The effect extends to how you process emotions socially, too. Differences in emotion recognition between people tend to shrink during high-estrogen phases, suggesting estrogen enhances the ability to read and respond to emotional cues. You likely won’t notice this during your period itself, when estrogen is still near its floor, but the groundwork is being laid.
How Birth Control Changes the Pattern
If you’re on hormonal birth control, the natural estrogen rise during your period doesn’t happen in the same way. Combined oral contraceptives suppress your body’s own hormone cycling and replace it with synthetic versions. During the placebo week (when you get a withdrawal bleed that mimics a period), both the synthetic estrogen and progestin drop. Unlike a natural cycle, there’s no FSH surge recruiting new follicles and no gradual estrogen climb from a developing follicle.
The synthetic estrogen in birth control pills, ethinyl estradiol, binds to estrogen receptors more strongly than your body’s own estradiol. This means the hormonal environment on the pill is fundamentally different from a natural cycle. One well-controlled study found that, unlike naturally cycling women, those on oral contraceptives didn’t experience the same phase-related differences in psychological well-being or physical performance. The hormonal highs and lows are essentially flattened.
Progestin-only methods eliminate the estrogen component entirely, and many people on continuous pill use skip the placebo phase altogether, meaning there’s no withdrawal bleed and no cyclical hormone pattern at all.
The Bottom Line on Timing
Estrogen reaches its cycle low right as your period begins, then starts a gradual ascent within the first few days of bleeding. The rise is modest while you’re still menstruating, picking up speed in the days after your period ends and peaking around ovulation. If you’ve noticed that the last day or two of your period feels different from the first, with slightly better mood or energy, that early estrogen climb is part of the reason. Your body is already preparing for the next ovulation before the current period is even finished.