Periods on the Keto Diet [aka Keto Shark Week]

  • Author: Katie
  • Date: October 9, 2022
  • Time to Read: 6 min.

Period talk is maybe something that you did not expect to be having when discussing the keto diet, however, this is a side effect that you need to be aware of! Some call it Keto Shark Week but is does not have to be something to be scared of. Read on and we will take you through what to expect.

Disclosure: Some of the links in this article may be affiliate links, meaning that we may earn a small commission if you click through using our link and make a purchase.  Please be assured that this will not cost you any extra money. Also, please be assured that we either use the products we recommend personally, or have been recommended by trusted friends who currently use them.

Firstly, let me preface this article with a reminder that none of us here at absolutely-keto are doctors.

Although we have decades of experience living a keto lifestyle and we have various nutritional qualifications between us, we are not qualified to offer medical advice.

Any changes to your period, or indeed, your health as a whole, you should seek professional medical advice.


This article is merely designed to give you an indication of what we, ourselves, friends, families, and readers have experienced when transitioning onto a keto diet.  

Why can the Keto Diet Impact your Menstrual Cycle?

There are a number of different opinions cited as to why the keto diet may impact your menstrual cycle.

With the keto diet or a low-carb diet, you tend to lose a lot of weight very quickly in the beginning. As you reduce your carbohydrate intake and increase the amount of fat that you are consuming, your body will transition into ketosis. Once in ketosis, you will see your weight loss gains.

Quick weight loss can lead to menstrual cycle irregularities. The hormonal changes caused by weight loss can impact your period.

This can also affect, ‘period pain’, for some people, this is reduced, for others, who have never suffered from period pain, may experience it for the first time in their lives (sorry!).

How Does Keto Affect Periods

Keto shark week is not something to be afraid of, read on to find out why.

If you are new to keto, check out this keto for beginners article.

We will run through a few scenarios below; 

If you are Overweight and quickly lose a lot of Weight

This is more pronounced in those people who are classified as obese based on their BMI, i.e. they have a BMI of 35 or over, check your BMI here.

The increased fat within larger people’s bodies produces extra estrogen. This additional fat is partly responsible for problems that you may experience with your periods.

For overweight people, losing weight is likely to help regulate your periods as your hormones come into balance. This is why overweight women are often encouraged to lose weight if they are struggling to get pregnant.

If you are Underweight and Gain Weight Fast

When we hear the term ‘diet’, our minds automatically go to people wanting to lose weight. However, ‘diet’ is only a reference to people undertaking a particular regime of eating. Keto can be a great option for people that are underweight and are needing to gain weight to get to a healthy BMI.

People who are underweight tend to struggle with getting their periods, again, due to hormonal imbalances in the body. This places the body under a lot of stress as it is constantly trying to make up for the imbalances. 

When an underweight person gains weight, their periods are more likely to come back and become regular.

Although the above changes to your menstrual cycle can be commonplace with the keto diet, the same is true for any drastic weight loss or weight gain on any diet. This is not exclusive to the keto diet.

Check out our article for other side effects of the keto diet and the health benefits of keto.

Should you be Worried if Keto Affects Your Menstrual Cycle?

Doctors will recommend seeking medical advice if there is any change in your health, including your period; which is always the best advice.

Missed periods can be a signal of a number of different health issues, which should not be taken lightly.

These medical conditions could include; hormone imbalance (distinct from that related to the gain/loss of weight), polycystic ovary syndrome (PCOS), this is why medical advice should always be sought.

Can you get your Period even if you are on the Pill or Coil when eating a Keto Diet?

There are forums and Facebook all over the internet with people in shock that they have got their period when eating keto, despite being on contraceptives with no periods for years.

There are also reports from women whose periods have stopped, due to age and thinking that they are going through menopause, getting their periods back.

Some women have reported spotting in-between periods too, thankfully, this always seems to be short-lived.

My experience of Keto and getting my period back.

I am one of those people! I have been on the pill for over a decade when I started keto. Periods were things of the past. I hadn’t had a period for years. I have never suffered from period pains as such, luckily!  

When I transitioned onto keto I got a very heavy period. It was at this point that I understood why people call it keto shark week!

This period was heavier than I had ever experienced previously, it was definitely in a new league to regular ‘shark week‘.

This was about a week into eating keto. Also, it was bright red, not the darker red I was used to (too much information, I know!)   This heavy period lasted for around three days, followed by a couple of lighter days.

I did not experience any period pain, however, I could feel my ovaries working. I know this is a very random thing to say, but I felt like everything was working right inside.

After this initial ‘flurry’ my period returned to ‘normal’ in that I did not have any further periods.

The only time I have experienced periods since this time is if I have fallen out of ketosis (usually when I have been traveling abroad) and then have had to get back into ketosis

The best bit? Getting my period is a good indication that I am back in ketosis! I do not need any fancy testing strips or machines! My period is my own personal ketosis tester!

How to Get Your Period Back to ‘Normal’ on when eating a Keto Diet

If you experience some irregularity with your periods when you first transition onto a keto way of living, carry on and keep eating keto! Your hormones will be unbalanced initially and then, with a consistent keto diet, your body will regulate its hormones and your periods should return to a regular pattern.

Keep Calm and Keto On!

How long will it take for your period to return to ‘normal?

Many women report it taking 3-6 months of eating a keto diet before their periods regulate themselves.

For some women, they will not have any side effects to their period, be it irregularity or pain.

Is there a good time to start the Keto Diet in relation to your Menstrual Cycle?

In short, there is no ‘best’ time to start keto in relation to your menstrual cycle. Start when suits you the best, be it when you’re at home and have the time to think about what you are eating.

Or, if you’re like me and need a distraction, start when you know you are going to be crazy busy and not have time to think about food

Final Thoguths

Eating keto may impact your periods, but this will be different for everybody. However, the one thing everybody can agree on is that eating a keto diet over time is more likely to lead to regulated hormones. Regulated hormones are key to having consistent periods.

This may not be the nicest topic to talk about, but share your experience in the comments below so we can all learn!

Leave a Reply

Your email address will not be published. Required fields are marked *

Skip to content