Common Keto Side Effects: Causes and Solutions
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Common Keto Side Effects: Causes and Solutions

Common Keto Side Effects: Causes and Solutions

Posted a year ago

Carb Manager Staff

Carb Manager Staff

Tony O’Neill, PT, DPT, MSc, RDN

Tony O’Neill, PT, DPT, MSc, RDN

Scientific Reviewer

Expert Approved

The Keto Diet is one of the most popular diet and lifestyle trends to emerge in recent years. 

And with the growing body of scientific research appearing to support the safety and health benefits, Keto is likely here to stay. 

However, a subset of individuals experience negative side effects on the Keto Diet, usually when first starting it. Luckily, most of these side effects can be mitigated by addressing a few gaps in your low carb, high-fat lifestyle. 

In this article from our Keto Beginners Series, we’ll talk about the most common Keto side effects and why they occur.

Most Common Side Effects

#1. The Keto Flu

The Keto Flu is a set of flu-like symptoms that typically occurs in the first week of going Keto. The symptoms can include fatigue, nausea, headache, and irritability. More on this below. 

#2. Sugar Cravings

It’s common for those going Keto to have intense cravings for sugary snacks in the beginning. These cravings are normal and are a result of your body getting less sugar than it is used to. You can think of this as a form of withdrawal symptom. 

But don’t worry! These cravings will diminish and disappear altogether as you become Keto-adapted. 

To help you make it through this early phase, see our article on Keto-friendly sweeteners and treats

#3. Decreases in Strength and Athletic Performance 

Your muscles need quick access to energy when exercising. That energy comes from stored glycogen and the phosphocreatine system. When you are starting the Keto Diet, you may experience a decrease in athletic performance. However, research has demonstrated that Keto-adapted athletes perform just as well as those on a carbohydrate-based diet.[*, *]

If you are very athletic, or interested in building significant muscle mass, check out our article about the targeted or cyclical Keto Diet. These modified Keto Diets may be a better option for those participating in higher-level training programs or bodybuilding. 

#4. Trouble Sleeping

Insomnia is a common side effect in the early stages of the Keto Diet. It has been postulated that the extreme dietary change can cause initial spikes in the stress hormone cortisol, which may interfere with sleep. 

Additionally, tryptophan is a precursor to serotonin and melatonin, which are thought to be important to sleep. The hormone insulin, which is released when you consume carbohydrates, plays a role in ushering tryptophan into the brain. When you’re on the Keto Diet, you have less insulin release, which may decrease the amount of tryptophan entering the brain.  

On the flip side, you may sleep less because the Keto Diet decreases fatigue. Studies have demonstrated decreased fatigue in overweight individuals, as well as those with narcolepsy.[*] Additionally, the Keto Diet, or at least weight loss in general, may help improve your sleep quality.[*]

So even if you are sleeping less, the quality of sleep, and your fatigue level throughout the day, could actually improve. 

If sleep is a problem as you adjust to Keto, you might consider eating a small amount of carbs before bed. You may also benefit from supplementing with melatonin and following common recommendations to maintain good sleep, such as going to bed at the same time every night, limiting caffeine intake in the afternoon, and avoiding screen time 1-2 hours before trying to sleep. 

#5. Increased Urination

Increased urination is a normal response to starting the Keto Diet. This is because eating low carb means secreting less insulin, and insulin plays a role in water retention. As discussed below, when you are eating low carb, you will hold onto less water, which means you will pee a lot more.

Causes of Side Effects on Keto

While there are many different symptoms that can arise when going Keto, they’re mostly the result of these common issues:

  • The adaptation process
  • Dehydration
  • Electrolyte deficiency 

These issues are all related and taking the right steps to fix them will help resolve most of your problems. 

When you first restrict carbohydrates, you’re depriving your body of the main energy source that it has operated on its whole life; glucose. You’re essentially taking glucose away and telling your body that it has to use fat instead. Well, your body uses fat for energy all the time, but it’s not used to using it as the PRIMARY source of energy. 

So, there are some changes your body needs to make in order to switch from glucose to efficiently using fat and ketones as its primary energy source, and it takes some time to make that happen.  

It only takes about 4-7 days to reach a state of ketosis,[*] while it can take between 30 days to 3 months to be fully Keto-ADAPTED.*, *]

For the first week of the Keto Diet, you may have symptoms of fatigue, brain fog, headaches, irritability, muscle cramps, lightheadedness, and nausea. These symptoms vary among individuals and will begin to improve as your body adapts to the new diet. It generally takes 1 week to 10 days for these symptoms to resolve. 

By the end of the second week, most Keto Dieters report improved energy, focus, and concentration. At this point, their bodies have made significant strides in adapting to efficient fat metabolism.    

Solutions: How to feel better as you adapt to ketosis

To EASE the adaptation process, make sure to drink PLENTY of water (>64oz), add salt to your meals, and include lots of non-starchy vegetables every day

Your body won’t retain water and electrolytes the same way it does when you’re eating a carbohydrate-based diet. In fact, the symptoms of low sodium (aka hyponatremia) and other electrolytes are very similar to the symptoms of the Keto Flu. Therefore, it’s reasonable to think that these two things are related, and you need to be more mindful about replenishing these vital elements of health through drinking more water, adding salt to your meals, and eating plenty of nutrient-dense veggies. 

The symptoms may also be related to lower than normal blood sugar levels early on. You might think of this as a kind of a withdrawal period. Your body will quickly adapt, and your blood sugar should remain within a healthy range as long as you are eating enough throughout the day. Your body is crafty and can make the glucose it needs from non-carbohydrate sources.   

These Side Effects Can Be Completely Mitigated with Time and a Properly Formulated Ketogenic Diet

While some of these side effects may discourage you... don’t let them! 

As long as you give your body some time to adjust to the Ketogenic diet, take the proper steps to keep your stress levels low, and maintain a proper electrolyte and mineral balance, you can greatly reduce -- or completely eliminate -- these Keto side effects.

Note: The content in this article is not medical advice and is intended for informational and educational purposes only. Always talk to your doctor before changing your diet.

Comments 31

  • FavorableCauliflower960741

    FavorableCauliflower960741 3 months ago

    I need some help. I have been on the keto diet for 2 months, everything has been great. Unfortunately, I have been throwing up at night, and have a rash that is itchy and sore. Any thoughts

    • rrodshell

      rrodshell 4 months ago

      Hi 🙋🏻‍♀️ I’m on day 9 and I don’t think I have had any symptoms… in fact the transition seemed to be fairly easy - 🧐 I lost 4 lbs on week 1. Am I doing something wrong after reading all these comments it’s got me thinking 🤔

      • SuperAvocado592033

        SuperAvocado592033 4 months ago

        The dizziness is the worst for me.

        • AmazingAvocado378553

          AmazingAvocado378553 5 months ago

          I wonder why no one really addresses the keto rash and no, it’s NOT rare!!!!

          • RousingMacadamia470664

            RousingMacadamia470664 6 months ago

            Have any of you had the Keto Rash? I dont see any information in here about that. :( any tips?

            • AmazingAvocado378553

              AmazingAvocado378553 5 months ago

              I’ve been dealing with a bad generalized rash for over 30 days. Got some black seed oil coming to take & apply.

          • Ross150

            Ross150 6 months ago

            Didn’t have a bad case of keto flu, but my sleep has been significantly disrupted. I drank a gallon of water the first two weeks of decreasing my carb intake and I think it helped me pass thru the Keto flu. But muscle aches are starting now that I decreased my water. I gotta start again!

            • AdelB

              AdelB 7 months ago

              Feeling a bit foggy and low energy today. Any tip? (Am already drinking a lot of water) the past thee days have been awesome and was feeling great.

              • Tsveta

                Tsveta 8 months ago

                It is my second month on Keto and U have lost 7 kg. Didn't have a Keto flue but I have now cramps and muscle akes. I am taking Kallium and Magnesium but still feeling not 100%. What do you suggest. Thank you

                • UnbelievableArugula948557

                  UnbelievableArugula948557 7 months ago

                  Take a potassium supplement along with B-1

                • MarvellousArugula513435

                  MarvellousArugula513435 7 months ago

                  There is these water drinks at Safeway. One with potassium one with magnesium you can try.

                • CasD383

                  CasD383 8 months ago

                  Potassium

              • NettieNice

                NettieNice 8 months ago

                Finding it hard to meet my fat intake ......what can I do ?

                • StellarAvocado298070

                  StellarAvocado298070 2 months ago

                  You only eat as much fat your body needs to stay full.

                • OutstandingArugula986995

                  OutstandingArugula986995 4 months ago

                  Dumb question but I’m new here … what is “bulletproof” coffe?

                • SuperRadish102616

                  SuperRadish102616 6 months ago

                  Take fish oil.

                • UnbelievableArugula948557

                  UnbelievableArugula948557 7 months ago

                  Bacon!!!!

                • AzLily2000

                  AzLily2000 7 months ago

                  If you drink coffee try making bullet proof. It uses MCT oil and Butter and heavy cream. Lots of healthy fat that way.

                • OutstandingKale930034

                  OutstandingKale930034 8 months ago

                  Add butter when you cook. It tastes better anyways.

              • xaniaim

                xaniaim 8 months ago

                Hey Guys! Wondering if any of you received any answers yet? I've been having the same kind of problems.

                • Katt Barrett

                  Katt Barrett 8 months ago

                  Been on Keto for 10 days and still feel terrible. Stomach ache and diarrhea. I hope this lets up soon. I am just in bed I feel so sick

                  • RemarkableKale834166

                    RemarkableKale834166 6 months ago

                    Stomach aches and diarrhea can be caused by Sugar Alcohol because they are laxatives. Sugar alcohols are popular in keto products.

                  • AmazingCauliflower233021

                    AmazingCauliflower233021 8 months ago

                    It takes our body’s time to adjust. Drink lots of water.

                • karensueburton

                  karensueburton 8 months ago

                  Been on keto 10 days. Diarrhea is still a frequent, daily thing. Is that part of keto flu?

                  • RemarkableKale834166

                    RemarkableKale834166 6 months ago

                    Diarrhea can also be caused by sugar alcohol because they are laxatives. Sugar alcohols are popular in keto products.

                  • AmazingCauliflower233021

                    AmazingCauliflower233021 8 months ago

                    Yes I have had it for quite awhile. Stay with it. Your body is changing and it will even out once your in Ketosis it is a beautiful thing. I have lost 55 lbs. I feel amazing and my doctor is is happy with all my blood test. It is worth it.

                  • Katt Barrett

                    Katt Barrett 8 months ago

                    Me too!

                • Manana

                  Manana 8 months ago

                  I have been on strict Keto for a month, started having sweet taste in a mouth. Is it because of Keto?

                  • UnbelievableArugula948557

                    UnbelievableArugula948557 7 months ago

                    I believe so since it was mentioned that a person’s breath would smell sweet

                • Sailormoon

                  Sailormoon 9 months ago

                  When does the increased blood pressure and heart rate normalize? Been on Keto 7 weeks

                  • UnbelievableRadish819060

                    UnbelievableRadish819060 7 months ago

                    Wondering as well