Why is my period late? 9 Possible Reasons

hormonal health Jun 03, 2019

Late period?

First things first, are you sure you aren't pregnant?


Ok, let’s cross that off the list...

I’m also going to assume that you're not breastfeeding and you aren't perimenopausal.

Also, how late is it? If you are just 2-3 days late, this is considered a normal variance in your cycle. A general rule of thumb is that if your period is delayed by 5+ days, that’s when it’s considered late.

Let’s narrow down what’s going on for you by looking at the most common reasons for late periods.

1. Are you eating enough?

Undereating is one of the most common causes of late periods. A 30-year-old sedentary woman needs 2000 calories a day just to maintain her health. Sedentary! If you’re exercising, you’ll need more than that.

Click here to see what 2000 calories a day looks like and consider logging your meals for a few days in My Fitness Pal to see how many calories you’re actually eating.

Here’s why eating enough matters:

The hypothalamus in your brain perceives restrictive eating as famine. Because your body is primal, it protects itself by delaying or shutting down ovulation. If there’s a famine, there definitely is not enough nourishment to grow a baby and keep you healthy at the same time. Delayed ovulation means a delayed period.

If you are trying to lose weight, you still need to be realistic with your calorie intake.

Also, if your period is late and you’re on a low carb diet or a keto diet, you may want to reconsider this. Women need carbs for a healthy menstrual cycle.

2. Are you exercising too often or for too long?

The combination of too much exercise and not enough food can lead to hypothalamic amenorrhea.

This is a condition where menstruation stops for several months due to your hypothalamus no longer communicating with your ovaries which leads to a reduction in hormone production.

Also, exercise is a form of stress for the body, keep this in mind as you read point number 5 below.

3. Are you underweight?

Being underweight or having a very low body fat percentage can cause a lot of menstrual issues including late periods.

If the idea of eating more and/or exercising less frightens you, you might need to consider if you have an eating disorder.

Please don’t be afraid to reach out for help, there are lots of women who understand you and know what you are going through. You might like to start here or here. And I’m sending you some love xx

If you’re overweight, your fat cells might be the issue

If you are overweight or have a high BMI, your late period could be due to an excess of estrogen. Estrogen is normally produced by the ovaries, but fat cells also produce it.

The more fat cells you have, the more estrogen you will produce and this can cause an imbalance in the ratio of estrogen to progesterone.

4. Is your sugar habit to blame?

A high sugar diet can cause a delay in, or prevent ovulation completely.

Let me quickly explain how imbalanced blood sugars cause hormonal issues:

High blood sugar is dangerous, so when sugar levels in the blood go up after eating, insulin is released to usher the sugar from your blood into your muscles and organs.

There, it’s either used as energy or stored as fat.

If you eat a high sugar meal or something with a lot of refined carbs, your insulin spikes high to get the sugar out of your bloodstream, this sudden spike in insulin causes your adrenal glands to release cortisol and adrenalin – your stress hormones!

A high sugar diet leads to a cascade of effects:

  1. High cortisol which leads to low progesterone.
  2. High adrenaline which can lead to adrenal fatigue.
  3. And of course, constant spikes in insulin leads to insulin resistance which can lead to diabetes.

If you have diabetes, you may suffer from a range of period irregularities, including long cycles, short cycles and heavy bleeding.

Also, insulin resistance can also lead to PCOS

There are several types of PCOS and the most common sub-type is Insulin Resistant PCOS. This is caused by lifestyle choices and obviously, a diet that is too high in sugar.

5. Is your period late because of stress?

Have you been feeling stressed lately?

Stress is one of the most common reasons for a late period.

I've already mentioned that stress leads to high cortisol levels but I haven't explained that stress actually affects all of the steroid hormones.

Have you heard of something called the ‘Pregnenolone Steal pathway'?

In very oversimplified terms it works like this:

Pregnenolone is the precursor to all steroid hormones (including cortisol, estrogen, testosterone and progesterone). Chronic stress means your body is producing a lot of cortisol and that means there isn't always enough pregnenolone left to make your sex hormones.

Plus, stress can elevate your insulin levels and as mentioned earlier when discussing sugar, this interrupts your ovulation.

It's a yucky cycle.

I've put together this post about anti-stress tips for women and it's been one of my most popular blogs.

If you want to really understand how stress affects your hormones and fertility I talk about it in more detail in this article.

6. Could it be your thyroid function?

If your thyroid is overactive this is known as hyperthyroidism and this can cause irregular periods.

Hypothyroidism is the opposite - this is an underactive thyroid and it too can cause irregular periods.

The thyroid is a very important gland and when it's not working how it should, it affects your production of Prolactin, Follicle stimulating hormone (FSH) and Luteinizing hormone (LH).

The health of your thyroid also affects your insulin sensitivity and plays a part in detoxification of estrogen.

If you want to learn more about thyroid health, this 10-minute video is a great overview.

7. Did you only recently start getting your period?

If your first period was within the last 2 years, it’s normal for you to have irregular periods. As a young woman, your body is still developing and it will take time for your cycles to become regular.

The first 12 months, in particular, can be quite sporadic and although things should start to regulate in the second year, cycles up to 45 days are still normal.

Cycles up to 45 days long are nothing to worry about as a teen.

On the other end of the scale, are you in perimenopause?

If you are in your 40’s, it’s possible that you have begun the transition from reproductive age to non-reproductive age. This is known as perimenopause.

If your period is late and you’ve noticed that over the past couple of months it seems to be different every cycle, you might be transitioning into menopause.

8. Is it your medication?

If you've recently started or stopped using a medication, this might be messing with your period.

All medications have side effects.

If you weren’t provided with sufficient information about the possible side effects of your medication, speak to your doctor.

Below is a list of medications known to affect your menstrual cycle:

  • Hormonal birth control
  • Anti depressants
  • Blood pressure medications
  • Chemotherapy
  • Allergy medications
  • Antipsychotics
  • Thyroid medications  

9. Are you using hormonal birth control?

Or maybe you've recently stopped using it? There’s a lot of different hormones that need to rebalance after you quit the pill and I wrote about them here.

When you’re on hormonal birth control there is a constant flow of synthetic hormones and every woman’s body reacts to this differently.

If you're still using hormonal birth control and you're having late periods, this is the first place you should be looking.



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