The most commonly prescribed medicine for a delayed period is medroxyprogesterone acetate, a synthetic form of progesterone taken by mouth for 5 to 10 days. It triggers a withdrawal bleed within a few days of finishing the course, effectively “resetting” your cycle. But the best option for you depends entirely on why your period is late, which is why figuring out the cause matters before choosing a treatment.
A period that’s a few days late is rarely a medical concern. But when your cycle disappears for three months or more without explanation, that’s clinically considered secondary amenorrhea and warrants evaluation. The treatments below address different underlying reasons for a missing period, and they work very differently from one another.
Progesterone to Trigger a Withdrawal Bleed
When a doctor wants to bring on a period quickly, medroxyprogesterone acetate (commonly known by the brand name Provera) is the standard choice. The typical dose is 5 to 10 mg per day, taken for 5 to 10 days. After you stop taking it, your uterine lining sheds and bleeding usually starts within a week.
This works because the medication mimics the natural rise and fall of progesterone that happens during a normal cycle. Your uterine lining builds up in response to estrogen each month. Progesterone normally signals the lining to mature and then shed. When your body isn’t producing enough progesterone on its own, the medication fills that gap. Once you stop taking it, the sudden drop in progesterone levels triggers the bleed.
There’s one important caveat: this only works reliably if your body is still producing estrogen. Progesterone needs an estrogen-primed uterine lining to act on. If estrogen levels are very low (below about 50 pg/mL), a progesterone course may not produce any bleeding at all. That result itself becomes diagnostic information, pointing your doctor toward different possible causes like premature ovarian insufficiency or a hypothalamic issue.
Progesterone brings on a single bleed. It doesn’t fix whatever caused the delay in the first place, so it’s often a first step rather than a complete solution.
Hormonal Birth Control for Ongoing Regulation
If your periods are chronically irregular and you’re not trying to get pregnant, combined hormonal contraceptives (the pill, patch, or ring) are one of the most effective ways to establish a predictable cycle. These contain both estrogen and progestin, which thin the uterine lining and create a controlled hormonal pattern your body follows.
The scheduled withdrawal bleeds you get during the placebo week aren’t true ovulatory periods, but they serve several purposes. They keep your uterine lining from building up excessively, which reduces the risk of endometrial hyperplasia. They also lower the long-term risk of uterine and ovarian cancer. For many people with irregular cycles, the predictability alone is a significant quality-of-life improvement, with periods that tend to be lighter and shorter.
Combined hormonal contraceptives are commonly prescribed for conditions like PCOS, stress-related cycle disruption, and unexplained irregularity. They’re a management tool rather than a cure, so periods may become irregular again after stopping.
Metformin for PCOS-Related Delays
Polycystic ovary syndrome is one of the most common reasons for chronically missed or delayed periods in reproductive-age women. In PCOS, insulin resistance plays a central role in disrupting ovulation. The body produces excess insulin, which drives the ovaries to overproduce androgens (male-type hormones), and that hormonal imbalance prevents eggs from maturing and releasing on schedule.
Metformin, an insulin-sensitizing medication originally developed for type 2 diabetes, addresses this root cause. By improving how your cells respond to insulin, it lowers circulating insulin levels, which in turn allows hormone balance to shift back toward normal ovulation. When ovulation resumes, periods follow. Studies confirm ovulation by measuring progesterone levels during the second half of the cycle, and metformin has been shown to restore regular ovulatory cycles in many women with PCOS.
Not everyone responds, though. Women with more severe insulin resistance may not see enough improvement from metformin alone, which suggests the medication can’t always overcome the metabolic disruption in heavily affected patients. It also takes time to work. You won’t see a bleed within days the way you would with progesterone. Most people need several months of consistent use before noticing a pattern shift.
Myo-Inositol as a Non-Prescription Option
For women with PCOS who prefer a supplement-based approach, myo-inositol combined with D-chiro-inositol has shown promising results. In a clinical trial of young women with PCOS, taking 550 mg of myo-inositol and 150 mg of D-chiro-inositol twice daily for six months led to spontaneous periods resuming in about 85% of participants. Average cycle length dropped by 54%, and roughly 27% of women achieved fully regular cycles (24 to 38 days) after six months, compared to none at the start of the study.
Inositols work through a similar pathway to metformin. They improve insulin signaling, which helps lower the excess insulin that drives hormonal imbalance in PCOS. The effect is milder and slower than prescription medications, but the side effect profile is also gentler. Inositol supplements are available over the counter in most countries, making them accessible without a prescription. They’re not a quick fix for a single late period, but they can meaningfully improve cycle regularity over several months of consistent use.
Chasteberry for Mild Hormonal Imbalance
Chasteberry (Vitex agnus-castus) is one of the most studied herbal remedies for menstrual irregularity, particularly when slightly elevated prolactin levels are involved. Prolactin is the hormone responsible for milk production, and even modestly high levels can suppress ovulation and delay periods.
Lab studies show that chasteberry acts on dopamine receptors in the brain’s pituitary gland, which reduces prolactin secretion. In one clinical trial of women with luteal phase defects (a shortened second half of the cycle), three months of chasteberry supplementation nearly doubled the length of the luteal phase, from about 5.5 days to 10.5 days, and dramatically increased progesterone production during that phase. The placebo group showed no change.
The evidence has limits, though. A review by the European Medicines Agency noted that the prolactin-lowering effect in humans hasn’t been conclusively proven across all studies, and it appears to depend on both the dose used and how elevated prolactin levels were to begin with. A single dose showed no measurable effect on prolactin or other hormones. Chasteberry is best suited for mild irregularities rather than prolonged amenorrhea, and it requires weeks to months of daily use.
Why the Cause Matters More Than the Medicine
A delayed period is a symptom, not a diagnosis. Progesterone can bring on a bleed in the short term regardless of the cause, but the right long-term approach depends on what’s actually happening in your body. PCOS, thyroid disorders, high prolactin levels, excessive exercise, low body weight, chronic stress, and perimenopause all cause delayed periods through completely different mechanisms. Treating PCOS-driven delays with chasteberry, or prolactin-driven delays with metformin, won’t produce meaningful results.
Basic evaluation typically involves blood tests for thyroid function, prolactin, and reproductive hormones like estradiol and FSH. If a doctor prescribes progesterone and you bleed afterward, that confirms your body is producing enough estrogen and the issue likely involves ovulation. If you don’t bleed, it points toward lower estrogen production or a structural issue, which changes the diagnostic direction entirely. This simple test narrows the possibilities significantly and guides treatment toward something that will actually work for your specific situation.