What to Expect On Your First Week of Keto

Here’s a list of what you can expect from your first week of keto – keto flu, insomnia, sugar cravings, and much more!

Starting your keto journey means that you are going to have the first week on keto. I will not sugarcoat this first week for you because it can be really intense. You don’t have to be afraid of this first week though – it goes as fast as it comes. Knowing what to expect can help you realize that what you are experiencing is normal and have some ways to prepare for this. Your body has been using carbohydrates for its entire life to give you energy. You may have even been addicted to sugar so your body could go into withdrawal. When you go on keto your body will have to learn how to use fat for energy. Your body will be confused until it realizes what to do. The first week of Keto is how your body learns how to use fat for energy and that your limited carbohydrate intake is nothing for your body to worry about. 

Here is what you can expect on your first week of Keto:

Flush of Weight Loss 

Pink Scale

Your body will go through a flush of weight loss. This is mostly water weight, but still really encouraging when you are starting a new diet! Don’t expect to lose this same amount each week though. You might lose anywhere from 10-15 lbs this first week! 

Keto Flu

Girl sick in bed

The Keto Flu is not really the flu, but it mimics flu-like symptoms. Keto Flu is caused by your body going into a shock from no carbs and sugars and relying on fat for energy. Your body will fight back on this until it realizes you are not in any harm from dying. Your body is smart and will adapt to use fat as its main energy source. 

You can expect to feel very tired and fatigued this first week. With fatigue comes headaches, irritability, brain fog, sugar cravings, dizziness, nausea, and cramps. This will only last about a week and after this feeling, you will feel so much energy! 

One way to combat the Keto-Flu is to make sure you are drinking plenty of water and getting enough salt! If you need to you can even make a keto electrolyte drink.

Stomach Issues 


Expect your stomach to be very confused. You may have the sense to go #2, but you may struggle. Constipation is very normal. You may also have “keto poops” this first week which is a runnier #2. 

Extreme Thirst

Girl Drinking Water

Each time I’ve gone into Keto I have an extreme thirst that first week. I drink a gallon or more of water because I cannot satisfy my thirst. Have enough water on hand! You’ll also pee a lot because of this. 

Sleep Issues

Girl sitting on bed

You will most likely experience insomnia during your first week. It could be hard getting to bed and this will cause you to be very tired in the mornings. 

After your first week of keto though, you’ll soon realize that you are sleeping better than ever and waking up with so much energy!

Sugar Cravings 

Plate of Donuts

You will have sugar cravings this first week. They can be very intense and you might think about bread, potatoes, and ice cream more than you ever had. Sugar is very addictive so when you cut your carbohydrates (which is a form of sugar), your body will be in withdrawal. Try to eat cheese and maybe even a keto ice cream if you cannot control the cravings. 

The sugar cravings do go away.

Extreme Hunger

Girl eating Potato Chips

I know the first week I was in Keto I was always so hungry! One night I ate half a tri-tip roast and still lost a few pounds overnight! Make sure you are eating enough. Eat as much protein as you need this first week. Being hungry will only make the Keto flu and these other symptoms worse. 

After the first week you’ll soon need less food to be full, but expect to eat more than normal. Have cheese and other keto snacks on hand, but don’t go over your carb limit. Proteins will help you stay full.

Bad Breath and Body Odor

Close up of sweaty neck

As your body goes into ketosis, your body will create Ketones (more on this in a later post). Ketones can cause bad breath and a different body odor to occur. This isn’t a problem after the first week as your body gets used to this, but expect this to happen. 

Knowing what happens in this first week of keto can help you prep for what is to come. If you are still working from home, you may be able to handle these issues. If you are starting keto and need to go into the office just make sure you have enough food and water! Try to start keto when you are off work as well. You won’t have the most fun time, but it won’t make your daily workday as bad either.


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