11 Reasons Why My Period Is Late – Even With A Negative Pregnancy Test

A late period can be caused by lifestyle, illness (including COVID-19), hormones, or even stress — and we’ll tell you everything to know.
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Updated:January 2024

Many of us are taught that a late period equals pregnancy, but that’s not always true — many factors relating to lifestyle, illness, hormones, and even stress can cause delayed menstruation.

Key Takeaways:

  • A late or missed period doesn’t always mean you’re pregnant.
  • A delayed period can result from a naturally irregular cycle, increased stress/anxiety, lifestyle changes, weight fluctuations, medications (including birth control or Plan B), puberty or recently started periods, illness (including COVID-19), extreme exercise or physical activity, breastfeeding, perimenopause, and chemical exposure.
  • If more than 35 days have passed since your last cycle, your period is considered late.
  • Irregular menstrual cycles are common but there are no proven medical ways to induce a period.
  • False negative pregnancy tests are rare but can occur.
  • Always see a doctor if you’re unsure about your late period, have additional symptoms, or think that you might be pregnant.

If you’re a woman, you’ve probably had the terrifying experience of a late period at least once.

I had quite the scare back in my college days after taking Plan B for the first time, which resulted in an out-of-whack cycle for the next couple of months.

When you first realize that your period is late, your thought process might quickly devolve from coherent to a paranoid stream of panic:

My period is late. Why is my period late? How late IS a late period? How late can a period be? How many days late can a period be before worrying about pregnancy? What the hell is going on with my body and how much do I need to worry?

Before you spiral, know that you’re not alone — many women have discussed having a late period on our forums (check those threads out here and here) — and we’ll explore all the reasons why it can happen, and what to do about it.

Reasons Why Your Period May Be Late

infographic featuring a concerned woman looking at a calendar with inset listing 11 possible reasons for a late period including a naturally irregular cycle, weight changes, lifestyle changes, recently started periods, medications, illness, stress, extreme exercise, breastfeeding, perimenopause, and chemical/pesticides

Although pregnancy is a possible explanation for a missed period if you’re sexually active and have no medical issues that would prevent conception, there are many other reasons why a period can be late.

If your period still hasn’t arrived but the pregnancy test came back negative, it may be due to:

  1. Natural cycle irregularities
  2. Stress and anxiety
  3. Changes in your lifestyle
  4. Weight fluctuations
  5. Medications
  6. Recently Started Periods
  7. Illness
  8. Extreme physical activity
  9. Breastfeeding
  10. Perimenopause
  11. Chemical exposure

We’ll explore each in further detail below.

Having A Late Period Due To An Irregular Cycle

You might be expecting your period on a certain day, but your body may have other plans — and your period may not actually be “late” after all.

Our bodies aren’t robots and a variety of factors can create irregular periods.

While menstrual periods usually last between four to seven days and occur every 28 days, irregular periods can vary based on medical disorders, hormone levels, and mental health.

According to Dr. Jaime Seeman, an OB-GYN on our medical review board, a variation of 2-3 days from month to month is perfectly normal.

“Even when periods have been predictable for a long time, it is not abnormal to occasionally have an abnormal cycle (e.g., a missed period or mid-cycle spotting),” she said.

You may have miscalculated the day it should have started — remember, always count from the first day of one period to the first day of the next.

A period calculator or app can help you stay on top of things if you’re comfortable using one, but an analog day planner or paper calendar is a safe option if you’re concerned about the privacy of your personal data.

Stress And Anxiety Can Cause A Late Period

Everyone feels stress sometimes, but particularly high stress levels can impact our cycles.

Some common causes can include stress or anxiety from the loss of a loved one, work-related stress, and major life events.

Our editor-in-chief, Alison Huff, noted her period was late during the final days leading up to her wedding.

“My period was about two weeks late just before I married my husband and I was convinced that I was pregnant because we weren’t exactly being careful or using birth control,” she explained.

“As it turned out, I wasn’t,” she continued. “My period started about 30 minutes before I walked down the aisle. I wish I were joking.”

She added that the stress of the upcoming wedding likely affected her cycle and the moment she was able to relax — after it was organized and practically underway — her period returned.

“The hypothalamus controls and coordinates more than just menstrual cycles, and will respond to changes in other hormones, such as cortisol (a stress hormone),” according to Dr. Christine O’Connor, a staff physician at Mercy Medical Center in Baltimore.

When an excess of cortisol is released, it can mess with normal levels of reproductive hormones.

Occasional bouts of stress are a part of life, but if you miss over two or three periods, consider talking to your healthcare provider.

How Lifestyle Changes Can Make Your Period Late

If you’re working a lot more, have been trying out a new diet, or are experiencing major jet lag, it could affect your period.

Dr. Seeman, an OB-GYN on our medical review board, said, “Anything that stresses the system like a change in sleep patterns, or just stress itself, can cause cortisol to push around the hormones that impact your cycle.”

Night owls: frequently staying up all night can also cause menstrual irregularities since it creates an imbalance in your melatonin levels, which are integral for a healthy period.

How Weight Changes Can Make Your Period Late

For many women, weight is often a stressful subject.

Our weight can also affect our reproductive hormones, which means your periods can be affected if you’re over or underweight.

According to Dr. Seeman, this is because fat cells contain an enzyme called aromatase that converts other hormones (like testosterone) into estrogen.

So the more fat cells you have the more aromatase activity increases, pumping out excess estrogen.

And if you’re underweight, the hypothalamus can suppress the menstrual cycle until proper nourishment is received, so eating more or consuming healthier foods can make a major difference.

Whether you’re overweight, underweight, or have had a sudden weight change, ovulation can be disrupted or not happen at all, which can manifest as a late or missed period.

A Late Period Can Be Caused By Medications (Including Birth Control)

Birth control pills combine different hormones (estrogen and/or progestin)  that stop your ovaries from releasing eggs.

Just how late can a period be on birth control?

There’s no set window, but taking them or discontinuing use can all affect menstruation cycles for up to six months.

Women who take birth control continuously or pills that eliminate periods altogether may not experience a period at all, and that’s ok.

For people who use hormonal IUDs, amenorrhea (absence of menstruation) is common.

Other medications that can mess with your cycle include blood thinners (like Warfarin), thyroid medications, epilepsy medications, antidepressants, chemotherapy drugs, herbal supplements, and even aspirin and NSAIDs (like Ibuprofen) when taken regularly.

Additionally, if you’ve wondered if Plan B can make your period late, the answer is yes — it can affect the timing of your cycle, causing it to come up to a week earlier or later.

A doctor or pharmacist will be able to tell you if missed periods are a possible side effect of any medications you’re taking or clarify if you’re actually pregnant after taking Plan B.

How Recently Started Periods Affect Menstrual Irregularity

Puberty takes time, and not all young women immediately have a regular 28-day cycle as soon as their periods begin.

It can take up to five years to establish a regular menstrual cycle.

If you’re re-starting periods after they’ve stopped — for example, if you were pregnant, breastfeeding, or ill — the same concept applies, although the timeframe may be different.

Bodies need time to adjust to new processes, and patience is key.

Illness (Including COVID-19) Can Cause Period Disruptions

Several illnesses can cause irregularities in your periods, including thyroid diseases (which affect your metabolism and weight and therefore your cycles), polycystic ovary syndrome (PCOS), ovarian cysts, and diabetes.

Based on recent discoveries, COVID-19 can also be a culprit for irregular menstrual cycles.

Both the illness and the vaccine can cause unexpected changes, including breakthrough bleeding, missed periods, or a heavier flow.

Illnesses like Coronavirus also increase stress and cause weight changes, both of which can impact your cycle.

If you recently had the flu, pneumonia, meningitis, a heart attack, kidney failure, or another illness that may have resulted in drastic weight loss, your periods may be affected for a few months — even if you’re no longer sick.

Finally, there are some menstrual conditions directly related to irregular or abnormal periods, including endometriosis and dysmenorrhea.

How Extreme Exercise Or Athletic Activity Can Delay Periods

Regular exercise is essential for your overall health and well-being, but extreme exercise can create an energy shortage that affects hormone production, especially when it’s accompanied by weight loss or restricted calorie intake.

Extreme exercise can also cause fluctuations in thyroid and pituitary hormones, which may affect menstruation.

This can happen to women who are already underweight and exercise frequently.

Although many athletes may think of the absence of menstrual periods as a perk, this can cause long-term health issues, and anyone who is already underweight shouldn’t work out for more than an hour or two daily.

Breastfeeding Can Delay Periods (But Shouldn’t Be Used To Prevent Pregnancy)

While breastfeeding, your body produces prolactin and oxytocin, hormones that stimulate milk production and letdown.

Dr. O’Connor, one of the OB-GYNs we spoke to earlier, said prolactin “signals that your body is still supporting a new infant, and may not want to dedicate resources to a pregnancy at that time.”

When you stop breastfeeding, your periods may take a few months to return to normal, and there’s no guaranteed time window.

It can occur as irregular, light, or missed periods.

This is known as lactational amenorrhea, and it’s simply a temporary phase that disrupts your menstrual cycle’s usual rhythm.

While some women consider breastfeeding to act as a form of birth control, this isn’t always effective, so a contraceptive should be used as a backup unless you want another little one on the way!

How Perimenopause Causes Late (Or Changed) Periods

Perimenopause is the time when your body is transitioning into menopause, and it marks the transition period between your reproductive age and your non-reproductive age.

It can happen as early as your mid-30s, though more typically, perimenopause starts in your 40s, and the first sign is often irregular menstrual cycles due to a decrease in estrogen.

During perimenopause, periods often differ from what a woman is used to and can be late, arrive more frequently, or be lighter or heavier than normal.

Other symptoms, like hot flashes, mood swings, and sleep disturbances often accompany perimenopausal period changes.

This process can last anywhere from two to ten years, and only when a period has been stopped for an entire year does it mean that you’ve officially entered menopause.

Studies Show Chemical Exposure Can Cause Menstrual Disruptions

Some studies have suggested that women who work with pesticides may experience adverse effects on the endocrine system, which creates and regulates hormones.

And before you worry, it’s unlikely that eating regular produce would have such extreme effects — just be sure to wash your fruits and veggies before consuming them.

Another study found that women working with organic solvents (including phenol and formaldehyde in a pharmaceutical setting) were more prone to experience menstrual disturbances compared to those not exposed to them.

Finally, a 2020 meta-analysis pored through several studies on environmental toxicant exposure (e.g., air pollution or parabens) effects on menstrual cycles and found:

  • Nitrogen dioxide (air pollution) was associated with longer follicular phases of the menstrual cycle
  • Exposure to air pollution during adolescence was associated with increased odds of menstrual irregularity
  • Carbon dioxide and nitric oxide emissions did not seem to affect menstrual cycle length
  • Cycle lengths were found to be longer among those exposed to polybrominated biphenyls (PBBs) although the analysis noted the numbers were not statistically significant
  • Paraben exposure was found to be associated with shorter menstrual cycles

The authors of the meta-analysis noted that “this is an important area of investigation given the reports of altered MCL (menstrual cycle length) with certain environmental exposures.”

Understanding Your Menstrual Cycle

infographic illustrating a typical 28 day menstrual cycle

Every month during the menstrual cycle, a woman’s uterine lining thickens.

Then, an egg is released from the ovaries, traveling down the fallopian tube.

If that egg is fertilized, implantation is attempted, and it’ll start to grow.

If not, the uterine lining is shed and you get your period.

Normally, a cycle lasts between 21-35 days, but this can vary from person to person.

A “typical” 28-day menstrual cycle looks like this:

  • Days 1-5: Menstrual bleeding
  • Days 6-14: Uterine lining becomes thicker
  • Day 14-19: Ovulation occurs and an egg is released from the ovary — fertilization may occur
  • Day 19-28: If no fertilization or implantation, hormonal changes occur and the uterine lining prepares to shed

A menstrual cycle’s first day is always counted as the day your period starts.

When Is A Period Considered Late?

If you don’t have a known condition or illness, a period might be considered late if it’s been over 35 days since your last menstruation began.

How Late Can A Period Be If You’re Not Pregnant?

A period can be between 3-7 days later than usual if you’re generally regular.

Healthy menstrual cycles often range from three to five weeks (21 to 35 days) in length, but this can vary widely from person to person.

Can You Induce A Late Period?

You might want to induce your period to get it over with before a special event, create more regularity in your cycle, or just hurry along a delayed process that’s giving you anxiety.

Many of us have googled “how to induce late period” at least once due to that impatience, but there’s no safe medical way to induce a period.

The only truly reliable way to control your periods is through the use of hormonal medications like birth control.

Some people try herbal supplements, but no FDA regulations on these currently exist and they may interact poorly with medications you’re currently taking.

Can A Negative Pregnancy Test Be Wrong?

A late period and a negative pregnancy test can be a confusing combination.

Pregnancy tests are meant to detect human chorionic gonadotropin (hCG), a hormone that is produced during pregnancy.

If you test too early, however, your hCG levels may still be too low to detect.

Plus, different tests have different sensitivity thresholds — not to mention specific instructions regarding the method and timing involved.

This study shows that although rare, false-negative urine pregnancy tests (including ectopic pregnancies) can be missed, especially in patients with vaginal bleeding or abdominal pain.

If your first at-home pregnancy test is negative but you still don’t get your period after a week, test again to ensure you didn’t take it too early.

Pregnancy tests should (generally) be taken first thing in the morning when urine is most concentrated and the results should be checked using a timer for the best accuracy — but always follow your test’s instructions to the letter.

Beyond at-home tests, it’s a good idea to see your physician if you’re unsure of the results.

When To See Your Doctor

Since you know your body better than anyone, trust your gut and if you feel like something just isn’t right, call your doctor.

It’s never a bad idea to get a professional opinion.

You may want to make an appointment if:

  • You’ve missed more than two periods in a row.
  • Your missed or late period is accompanied by other symptoms.
  • You experience headaches, vision changes, fevers, hair loss, or excess hair growth.
  • You experience bleeding between menstrual cycles or after sex.
  • You’re still bleeding after the age of 55 or are experiencing post-menopausal bleeding.

Closing Thoughts

What counts as a late period can vary from woman to woman.

The only predictable thing about periods is how unpredictable they can be.

Trust your gut since you know your body better than anyone.

If you feel like something just isn’t right or if your period doesn’t start despite a negative pregnancy test, call your doctor for an appointment.

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