Missing your period for several months has a name: secondary amenorrhea. It’s clinically defined as going without a period for three or more cycle lengths if your cycles were previously regular, or six months if they were irregular. The causes range from pregnancy to stress to hormonal conditions, and most of them are treatable once identified.
Rule Out Pregnancy First
This might seem obvious, but it’s the most common reason for a suddenly missing period, and it’s the easiest to check. Home pregnancy tests detect the hormone hCG, and they’re highly accurate when used after a missed period. By the time you’ve missed several months of periods, hCG levels in a pregnant person would be extremely high (often above 32,000 µ/L by 8 weeks), so a home test at this point is very reliable. If the test is negative and you’ve truly missed months of periods, something else is going on.
Stress, Undereating, and Overexercising
One of the most common reasons younger women lose their period is something called functional hypothalamic amenorrhea. Your brain has a control center that sends hormonal signals to your ovaries telling them to release an egg each month. When your body is under significant stress, whether from psychological pressure, not eating enough, losing weight, exercising heavily, or some combination of these, your brain dials down those signals. Without that hormonal trigger, your ovaries don’t ovulate, and your period stops.
The mechanism is straightforward: your body reads these stressors as a sign that conditions aren’t safe for a pregnancy. Hunger hormones rise, the stress hormone cortisol stays elevated, and levels of leptin (a hormone tied to energy stores) drop. All of these changes suppress the reproductive signal at its source. This isn’t just a problem for elite athletes. It can happen to anyone restricting calories, going through a difficult time emotionally, or pushing hard at the gym without fueling adequately.
The 2025 update to the Female Athlete Triad guidelines highlights that this kind of energy deficiency doesn’t just stop your period. It can weaken your bones over time by lowering estrogen levels, increasing the risk of stress fractures. The guidelines also note that getting your period back once isn’t the finish line. Full recovery requires multiple consecutive normal-length cycles, because early returning cycles often don’t include actual ovulation.
Polycystic Ovary Syndrome (PCOS)
PCOS is one of the most common hormonal disorders in women of reproductive age, and irregular or absent periods are a hallmark. The condition involves higher-than-normal levels of androgens (often called “male hormones,” though all women produce them in smaller amounts). These elevated androgens interfere with ovulation, which is why periods become unpredictable or disappear.
Signs that point toward PCOS include excess facial or body hair (the single strongest predictor of elevated androgens, according to international guidelines), persistent acne, and hair thinning on the scalp. You don’t need all of these to have PCOS. Diagnosis typically requires two out of three features: irregular or absent periods, signs of elevated androgens (either visible symptoms or confirmed on bloodwork), and a characteristic appearance of the ovaries on ultrasound or elevated levels of a hormone called AMH. It’s worth noting that you can still have PCOS even with somewhat regular cycles, because ovulation can fail to occur even when bleeding happens on schedule.
Thyroid Problems and High Prolactin
Your thyroid gland, located in the front of your neck, sets the pace for your metabolism. When it’s underactive (hypothyroidism), the ripple effects reach your reproductive system. An underactive thyroid can raise levels of prolactin, a hormone normally responsible for milk production. When prolactin climbs too high, it blocks the hormonal signals that trigger ovulation, specifically FSH and GnRH, and your period can stop.
High prolactin can also occur on its own, sometimes caused by a small, benign growth on the pituitary gland in the brain. Clues that prolactin might be the issue include milky discharge from the nipples when you’re not pregnant or breastfeeding, and in some cases, headaches or vision changes (because the pituitary gland sits right behind the eyes). Both thyroid levels and prolactin are checked with simple blood tests, and both conditions respond well to treatment.
Medications That Stop Periods
Certain medications can suppress your cycle as a side effect. Hormonal contraceptives are the most obvious: some birth control pills, hormonal IUDs, implants, and injections are designed to thin the uterine lining, and many women on these methods stop bleeding entirely. This is generally not harmful, but it can be alarming if you weren’t expecting it.
Antipsychotic medications are another common culprit. Studies have found that 11 to 35% of women treated with various antipsychotics experience amenorrhea, with some medications carrying a higher risk than others. These drugs can raise prolactin levels, which blocks ovulation the same way a pituitary issue would. If you started a new medication in the months before your period disappeared, it’s worth asking your prescriber whether this could be a side effect.
Perimenopause and Early Menopause
If you’re in your 40s, skipping periods for months at a time could be perimenopause, the transition phase leading up to menopause. During perimenopause, your ovaries produce estrogen less predictably, so cycles become irregular, sometimes skipping months before returning. This phase can last several years before periods stop permanently.
If you’re between 40 and 45 and your periods have stopped, that’s considered early menopause. If you’re under 40, it’s called premature menopause or primary ovarian insufficiency. Premature menopause affects about 1 in 100 women and can happen without any obvious trigger, though it sometimes runs in families or results from autoimmune conditions, surgery, or certain medical treatments. A blood test measuring estrogen and related hormones can help determine whether your ovaries are winding down earlier than expected.
Symptoms That Need Prompt Attention
A missing period on its own usually isn’t an emergency, but certain accompanying symptoms suggest a cause that needs evaluation sooner rather than later:
- Milky nipple discharge (when not pregnant or breastfeeding) points to elevated prolactin
- Headaches or vision changes can signal a pituitary growth
- Rapid or excessive hair growth on the face and body suggests significantly elevated androgens
- Pelvic pain may indicate a structural issue
- Significant recent weight loss raises concern for energy deficiency affecting your bones
The general guideline is to seek evaluation if you’ve missed three consecutive periods when your cycles were previously regular. If your cycles were always irregular, six months without a period is the threshold.
What to Expect at the Doctor
A typical workup starts with a pregnancy test, then blood tests checking thyroid function, prolactin, and androgens. Your doctor will ask about your stress levels, eating patterns, exercise habits, recent weight changes, and any new medications. Depending on the results, you may have an ultrasound of your ovaries to look for features of PCOS, or further hormone testing to assess whether your brain’s signaling to your ovaries is functioning normally.
For stress-related or exercise-related amenorrhea, treatment centers on addressing the root cause: eating more, reducing training intensity, managing stress, or some combination. For PCOS, treatment depends on your goals and might involve hormonal therapy or lifestyle changes. Thyroid issues and high prolactin are typically managed with medication that brings hormone levels back into range, often restoring cycles within a few months. The important thing is that nearly all causes of missing periods are identifiable with straightforward testing, and most are reversible.