11 Reasons Why My Period Is Late – Even With a Negative Pregnancy Test
Are you scared or confused because your period is late but you’re NOT pregnant? Discover 11 common reasons why Aunt Flo may be late to the party.
Sign Posted On A Tree By Woman Looking For Her Late Period
Melissa Drumm
Dr Jaime Seeman

Wait a minute. What’s the date?

I’m late.

Why am I late?

I’m never late!

Oh my God.

OH.MY.GOD.

What if…?

That was, give or take a few curse words, the first thing that ran through my mind when one fall weekend of my freshman year of college, my period was late.

My thought process quickly devolved from coherent — When was my last period? Was it on time? Maybe it’s just a really light month — to panicked — I’m not ready to be pregnant! And I’m definitely not ready for a baby! HOW WILL I TELL MY PARENTS?!

I ran to a friend and begged her to go with me to the pharmacy.

I couldn’t face that overwhelming pregnancy test display, not to mention standing in the checkout line with it in my hand, alone.

(Tangent: Honestly, even many years later, when I was actually trying to get pregnant, I found buying a pregnancy test totally nerve-wracking and strangely embarrassing. Maybe it was because of this previous experience, and the negative associations I made when I was 18. Have you felt this way?)

When we got back to the dorm — thankfully, having avoided seeing anyone I knew — I held the box in my sweating palms and read the instructions.

Feeling a little nauseous (IS IT MORNING SICKNESS?!?!?), I shut myself in the tiny bathroom stall, peed on the stick, then wrapped it in a paper towel to walk back to my room.

My friend talked me off the ledge while we waited an excruciatingly long two minutes for the line — or lines — to appear.

Negative.

A few days later, I got my period.

The thing is, this isn’t a unique or unusual story. This happens to tons of women, every single day.

In fact, lots of them have posted about it on Women’s Health Interactive’s forums (check out a few examples here, here, and here).

While I never figured out the reason my period was late, I’ve since found out that there are dozens of reasons that it might happen — and pregnancy is just the tip of the iceberg.

So if you’ve been here — no period, with a negative pregnancy test — first, take a deep breath and know you’re not alone.

Whether you’re nervous about a potential unexpected pregnancy or excited that you may be pregnant, there are plenty of others who have been in your shoes.

I spoke with a few medical experts to get their take on some of the things that can cause missed or late periods.

Read on to find out why Aunt Flo didn’t arrive when she should have — and whether or not you need to be concerned about it.

Article Summary:

Do You Know Your Cycle?

  • A normal cycle varies month-to-month between 21 to 35 days
  • Yours may also vary — even if it’s normally regular!

Why Is My Period Late If I’m NOT Pregnant?

  • Irregular Cycle
  • Stress & Anxiety
  • Schedule or Lifestyle Changes
  • Weight Changes
  • Medications, Including Birth Control
  • Recently Started Periods
  • Illness
  • Extreme Exercise
  • Breastfeeding
  • Perimenopause
  • Pesticides and Other Chemicals 

Know Your Cycle

First things first: If you’re like me, everything you learned about menstrual cycles in middle school health class has receded to a far corner of your brain, so let’s talk for a minute about what actually happens when you get your period.

Over the course of each month, the lining of your uterus — called the endometrium — grows thicker and is enriched with nutrients and blood to prepare for a possible pregnancy.

Around the middle of your cycle, an egg is released from one of your ovaries and travels down your fallopian tube.

If the egg is fertilized, it will attempt to implant itself in the lining of your uterus and begin to grow.

If it’s not fertilized or doesn’t implant, hormonal changes signal that it’s time to shed your uterine lining, and you get your period.

Basically: A lot has to happen for you to get your period.

The length of your cycle is measured from the first day of one period to the first day of the next one. A “normal” cycle can be between 21 and 35 days long, and it can vary from month-to-month.

Infographic Illustrating A Typical 28 Day Menstrual Cycle

(Click image to enlarge)

What A “Typical” 28-Day Cycle Looks Like

  • 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 uterine lining prepares to shed

If you want a more detailed description of this process, click here.

There are a bunch of different hormones involved in menstruation — estrogen, gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone, progesterone — and they’re all interdependent (so the presence of one might stimulate the production of another).

Your period depends on these hormones working in perfect harmony, so when they’re out of whack, it can wreak havoc on your cycle.

As you’ll see, there are dozens of things that can throw a wrench into that delicate hormone balance, delaying or preventing the arrival of your period.

Side note: Did you know your cycle even plays a large role in your libido? Yep, it’s true.

So let’s get to the point: What are the things I wish I had known as a college freshman? And what are the things that can disrupt your hormones and cause your period to be late (or missed altogether)?

11 Reasons Why Your Period Might Be Late Or Missed Altogether

Infographic Of Concerned Woman With A Late Period And 11 Possible Causes

(Click image to enlarge)

Icon With Three Arrows Going In Different Directions Illustrating Irregularity

An Irregular Cycle

You might be expecting your period on a certain day, but your body may have other plans — that is, your period may not actually be late at all.

When you plant a seed in the ground, the plant never grows the same way twice. Each menstrual cycle in a woman’s body is a new fresh start and fluctuations in a woman’s body from month-to-month will surely impact it, including the length. Sometimes shorter and sometimes longer, but this is very normal.” Dr. Jaime Seeman, OB-GYN

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

Or perhaps your periods aren’t as regular as you thought.  

According to Dr. Seeman, who sits 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 tells us.

And remember, the symptoms of PMS and pregnancy can be pretty similar — fatigue, sore boobs, cramps, etc. — so try not to jump to conclusions too quickly.

Icon Of A Woman Showing Signs Of Being Stressed Or AnxiousStress And Anxiety

Realistically, we all feel stressed sometimes, but particularly high stress levels can have an impact on your cycles.

Ashlee, our Editor-in-Chief here at WHI, experienced this firsthand: “After the unexpected death of a loved one, I went nearly two months without getting my period,” she confided to me while I was writing this article.

Dr. Christine O’Connor, Director of Well-Woman and Adolescent Care at Mercy Medical Center in Baltimore, Maryland, shared with Women’s Health Interactive that “the hypothalamus controls and coordinates more than just menstrual cycles, and will respond to changes in other hormones, such as cortisol (a stress hormone).”

So when there’s an excess of cortisol being released, it can mess with normal levels of reproductive hormones. It makes sense — your body knows that high-stress levels aren’t conducive to a healthy pregnancy.

An Icon Showing A Clock With Arrows Going Around It ClockwiseSchedule Or Lifestyle Changes

Have you just taken on a second job and are working a lot more hours, or have you been working more night shifts lately?

Maybe you went on vacation halfway around the world, and have been suffering from jet lag ever since you got back?

Did you finally decide to try out that new diet your friends have been talking about?

Guess what? It may be impacting your periods!

“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”Dr. Jaime Seeman, OB-GYN

Icon Of A Scale With 2 Feet Illustrating Someone Measuring Their WeightWeight Changes

If you’re like me (and let’s be real, most other women) maintaining a healthy weight is already something you think about a lot.

And as if it’s not stressful enough already, your weight can also affect your hormones, which means your periods are going to be affected if you’re over or underweight.

When I asked Dr. Seeman why this happens, she said it 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.

Conversely, “if you are underweight, the hypothalamus [the part of the brain that controls hormone production] will suppress your cycle until your body signals that it is getting the nourishment it needs,” Dr. O’Connor, tells us.

Whether you’re overweight, underweight or have had a sudden change in weight, ovulation can be disrupted or not happen at all.

And if ovulation is delayed or skipped, guess what else will be delayed or just not show up at all that month?

That’s right. Aunt Flo!

An Icon Of Pills To Symbolize Medications Including Birth ControlMedications, Including Birth Control

The most obvious medication that can impact your periods: hormonal birth control, like the pill, an IUD, or an injection (like Depo-Provera).

That’s kind of the point, right?

But while birth control can help to regulate your cycle so it’s more predictable, the first 6 or so months after starting (or stopping) those medications will be an adjustment for your body, so some irregularity is to be expected.

Plus, some hormonal birth control methods actually eliminate periods altogether or work so that you get your period only every three months instead of every month.

Ask your doctor if the birth control you’re using might have these effects so you’ll be prepared — and if it’s something that makes you uncomfortable or nervous, try a different birth control method.

(Side note: By the way, if you’re wondering, my best guess as to what happened when I was a college freshman? I was pretty lax about taking my birth control. I was on the pill, and I often forgot to take it and would then double up the next day, or took it at a different time on the days I managed to remember it at all. Talk about messing with your hormones!)

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

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

An Icon Of A Red Droplet Symbolizing Menstrual BloodRecently Started Periods

When you start puberty and first get your period, it can take a while — sometimes from 2-5 years, according to Dr. O’Connor — for your body to settle into a “regular” cycle.

I remember when I first got my period and for the first couple of years, it took me by surprise every time. A lot of ruined undies later, it finally settled into a pattern.

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.

Give your body time to adjust, it’s been through a lot, and the best thing you can do is be patient and take care of yourself.

An Icon of A Woman CoughingIllness

There are a number of illnesses that 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.

Your doctor can help diagnose and control any of these chronic issues.

Acute illnesses can cause irregularities with your periods, too.

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.  

An Icon Of A Woman RunningExtreme Exercise

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.

For example, when Ashlee, WHI’s Editor-in-Chief, was in high school, she took up running. “I was already underweight, so within a few weeks of running, I had already lost so much body fat that I stopped having my period.” Living proof that these types of changes can happen quickly.

While, as an athlete, having no period can actually seem like a benefit, it’s not healthy long-term and shouldn’t be ignored.

An Icon Of A Woman Breastfeeding Her BabyBreastfeeding

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

“Prolactin…signals that your body is still supporting a new infant, and may not want to dedicate resources to a pregnancy at that time,” Dr. O’Connor told me. And when you stop breastfeeding, your periods may take a few months to return to normal.

In fact, after breastfeeding my son for 6 months, I still had not resumed having a period!

When I asked my doctor when I could expect my period to return, she said, “I don’t know. No one does.” Yup, hormones even baffle doctors sometimes.

An Icon Of The Female Venus Symbol With A ClockPerimenopause

Perimenopause is the span of time when your body is transitioning into menopause.

It can happen as early as your mid-30’s, though more typically perimenopause starts in your 40’s.

This transition can take a few months or a few years, but the first sign is often irregular menstrual cycles, thanks to — you guessed it — hormones.

Perimenopausal period changes are often accompanied by other changes, like hot flashes, mood swings, and sleep disturbances.

Icon Of A Bottle Of Chemicals Or PesticidesPesticides and Chemicals

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

But don’t worry — it’s unlikely that eating regular produce would have such extreme effects.

A Few Notes On Pregnancy Tests

Home pregnancy tests, when used correctly, are fairly accurate, but keep in mind that timing is everything.

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

If you test too early, your hCG levels may still be too low to detect. Plus, different tests have different sensitivity thresholds.

If your first test is negative but you still don’t get your period after a week, test again, just to be sure.

In Conclusion

Basically, hormones are fickle, fussy little bitches.

There, I said it.

But really, it’s pretty easy to throw your hormones out of balance.

The only thing predictable about hormones is how unpredictable they are. Just remember, take care of yourself and your hormones will generally follow.

Finally, since you know your body better than anyone, trust your gut. Do you feel like something just isn’t right? Call your doctor. It’s never a bad idea to get a professional opinion.

One rule of thumb, however: If you miss two or more periods in a row, it’s definitely time to see a doctor.


Have you ever missed your period for one of these reasons? Is your period late right now? Are you scared or nervous? Don’t worry, we’re here for you!

We’ve set up a forum to discuss this topic and answer any questions you might have when you need it most — whether you’re hoping for a period or a pregnancy.

Just click on the “Discuss” link/button that appears at the end of this article to lend your voice to the discussion.

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About The Author

Melissa Drumm
I'm Melissa, a writer and wordsmith, women's health enthusiast, and recently inducted member of the world-renowned Eyes-In-The-Back-Of-My-Head Organization as director of Don't-Make-Me-Come-In-There-And-Find-It-Myself, though...

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