Fact Checked by

Randall Evans, MS, RDN, LD

Keto Side Effects: How To Minimize & Avoid The Risks

Want to learn more about the side effects of a keto eating plan? Check out this list of mild and severe side effects experienced by those who follow a low-carb, high-fat diet for the first time.
Side effects of keto diet


The keto diet has been hailed for its ability to provide benefits such as weight loss and improved mental clarity. But this diet also comes with side effects you should be aware of, and they range from minor to major.

Table of Contents 
Why You Experience Side Effects on Keto
Mild Side Effects of Keto Diet and Remedies
Frequent Urination
Sugar Cravings
Keto Breath
Flu-Like Symptoms
Sleep Issues
Increase in Cholesterol
Severe Side Effects of Keto Diet and Remedies
Vitamin Deficiency
Disruption of Menstrual Cycles
Common Challenges Keto
Who is Keto Best For?
Who is Keto Potentially Dangerous For?
Keto Diet FAQs

When done correctly, the keto diet has a lot of benefits to offer.

However, this diet may also come with a few side effects.

Keto’s list of benefits includes:

  • Weight loss
  • Mental clarity
  • Greater energy
  • Decreased cravings
  • Muscle growth
  • Clearer skin

But truth be told, following the diet as a newbie can be scary – especially after you hear about keto side effects.

Don’t be intimidated because in this guide, you’re going to learn why side effects happen, what side effects you can expect, and how to effectively deal with them.

Why You Experience Side Effects on the Keto Diet

Switching from a typical high-carbohydrate to a low-carbohydrate diet lowers your body’s blood sugar levels. When your blood sugar is low, your body turns to its stored fat to meet its energy needs.

Fat gets broken down into molecules called ketones. On the keto diet, ketones become your alternative fuel source, which have been found to be more efficient than glucose since they provide more lasting energy.

Keep in mind that it takes time for your body to get used to utilizing ketones as its fuel, which explains why side effects happen.

Think of it as an adjustment phase, which is normal for anyone who tries anything new in life! The good news is that you don’t have to endure keto diet side effects – there are ways to minimize them and feel better.


Side-effects show up because your body is adjusting to a new energy source, but the side effects are manageable!

Mild Side Effects of Keto Diet and Remedies

Side effects of keto diet

1. Frequent Urination – very common

You will find yourself urinating more often as you start a keto diet. This happens because your body uses up its glycogen (stored glucose aka carbohydrates). Glycogen holds water in your body, which is why you release water by urinating.

Why does it matter? Frequent urination can be a problem because it may lead to dehydration. You can also lose electrolytes in the process.


  • Keep your water intake high. Here’s a helpful tip to know your hydration status: Check the color of your urine! A clear or pale color means that you are well-hydrated. Dark urine means that you need to drink more water.
  • Prevent electrolyte imbalances by eating low-carb foods that contain electrolytes such as sodium, potassium, calcium, and magnesium. Examples are salty snacks, green leafy vegetables, salmon, and cheese.

2. Sugar Cravings – very common

Do you have a sweet tooth? If so, your sugar cravings are going to be more intense as you drastically reduce carbs in your diet! Sugar cravings can make you feel weak and anxious. But don’t worry, there are ways to fight these cravings.


  • Often sugar cravings result from a lack of protein and fat in your keto diet. Replace those carbs with foods that are packed with protein and healthy fats such as whole eggs, meat, nuts and seeds, and fatty fish.
  • Engage yourself in an activity that takes your mind off those sweets. Research shows that going for a short walk actually reduces sugar cravings.
  • Another tip that will help is to make sure you’re getting enough fiber. When you cut out carb-heavy foods like pasta, and starchy vegetables like corn and sweet potato, you also miss out on fiber which can help curb sugar cravings. Try introducing more foods to your diet that are keto-friendly and contain fiber like spinach, broccoli, zucchini, avocado, and raspberries. You’ll find that with these foods you’ll stay fuller longer which will help conquer cravings.

3. Bad Breath “Keto Breath” – very common

Ever notice that your breath smells nasty? Don’t be surprised – bad breath on a keto diet, also known as “keto breath,” is expected. Keto breath is often described as having a “metallic” or “fruity” smell to it. While keto breath is a good sign that you’ve reached ketosis, it can be bothersome to you and other people who notice.


  • It may take weeks before keto breath disappears (Up to 21 days). Meanwhile, you can reduce bad odor by drinking more water, brushing and flossing your teeth daily, and taking sugar-free breath mints.

4. Flu-Like Symptoms – very common

You may have heard of “keto flu” but are not sure what it means. Keto flu is a collection of symptoms that kicks in on the first or second day of doing keto. Think of it as your body’s withdrawal reaction to carb restriction in your diet!

These flu-like symptoms include headaches, tiredness, brain fog, sore throat, and muscle soreness.


First of all, know that keto flu can go away in a few days.

  • If you find yourself too weak to work, allow your body to rest. A good night’s sleep of at least 7 hours will reduce your symptoms.
  • Increase your fat intake as well. Remember:

More dietary fats = more ketones in your body = fewer keto flu symptoms.

  • Supplement with MCT (medium-chain triglycerides) oil, a pure form of fat. Take one tablespoon straight up or add it to your cup of coffee.

5. Sleep Issues – common

The ketogenic diet can interrupt your sleep and cause insomnia, but only in the short term. However, we all know how much being sleep deprived can mess with your focus, energy and productivity.

Sleep researchers have confirmed that inefficient sleep is not only detrimental to your health but also impairs judgement, mood and your ability to learn and retain information.


Effective sleep comes down to a few simple practices and avoid some bad bedtime habits:

  • Eating very late at night. When you eat too close to going to bed, it can cause indigestion which affects sleep quality and your ability to stay asleep. Instead, set a hard stop on your last meal and snacks. This will prevent overeating and improve your sleep.
  • Exercising later in the day. When you exercise your brain releases adrenaline which stimulates your body and mind. By exercising closer to bed time it takes longer for your body to stabilize adrenaline levels which can make it hard to fall asleep. If working out is part of your daily routine, make sure it’s no later than 4 hours before you’re getting ready for bed.
  • Using your phone or computer before bed. There has been extensive research done on how blue-light from our devices trick our brains into delaying the onset of melatonin (the sleep chemical your brain releases) and negatively affects quality of sleep for up to an hour once you have fallen asleep. Instead, try “night shift” on your phone or use some blue-light blocking glasses before bed. You’ll look smarter and sleep better.

You can also keep your room cool. The ideal temperature for your body to fall asleep is between 60-67 degrees fahrenheit.

Put a few drops of lavender oil on your pillow. Studies have shown a link between lavender oil and sustained sleep.

6. Diarrhea – common

Yes, some new keto dieters may experience diarrhea. Diarrhea happens as a result of consuming more fat – which is a must on keto. Meanwhile, diarrhea can also be a side effect of consuming erythritol, a keto-friendly sweetener.

Stopping diarrhea is important to prevent dehydration. And it’s never fun to get stuck in the bathroom.


  • You may need to reduce certain fats in your diet, such as MCT oil. If you take more than one tablespoon of MCT, you’re likely to get diarrhea. Give your tummy time to adjust.
  • If you’re struggling with this, try drinking bone broth. It’s packed with nutrients like collagen (good for muscles, skin, bones), and zinc (immune booster). It soothes your digestive system, is easy to digest, and also helps digest other foods.

7. Constipation – common

Constipation is another digestive issues that’s caused by limited fiber in your diet. Because as we stated earlier, carbs are present in many high-fiber foods you’re familiar with such as whole grains and fruits. The good news is, constipation on the keto diet is very easy to deal with and prevent.


  • Similar to our suggestion for sugar cravings, boosting your fiber intake through keto-friendly foods like flaxseed, avocados, cauliflower, and chia seeds will make a big difference.
  • Going on brisk walking after a meal, increases blood circulation which has been shown to help with constipation.
  • Lastly, drinking more water. When you’re dehydrated water is pulled from your large intestine to serve other parts of the body where water is essential. This often causes constipation because it makes your stool more firm, and dry. By making sure you’re hydrated (about 10 cups a day), it makes easier for the body to pass stools.

8. Increase in Cholesterol – uncommon

There are people whose cholesterol levels increase on a keto diet. And because keto is high-fat, many falsely assume that it increases bad cholesterol and causes heart disease.

Yes, cholesterol levels increase, but one should look at specific cholesterol components. If you eat healthy fats on keto, then you should expect your good cholesterol (HDL cholesterol) to increase – which is a good thing. At the same time, your bad cholesterol (LDL cholesterol) decreases.

This beneficial effect of the keto diet on cholesterol was demonstrated by a study done on obese patients.


  • If you have problems with your cholesterol despite following a clean keto diet (meaning, you choose healthy sources of fat and eat whole foods), you might want to check with your doctor to rule out medical conditions. Some medical conditions elevate cholesterol, and your diet may have nothing to do with it.

Severe Side Effects of Keto Diet and Remedies

9. Vitamin Deficiency – uncommon

Not eating nutrient-dense, low-carb foods can increase your risk for vitamin deficiencies. Possible deficiencies include vitamin A, B vitamins, vitamin C, and vitamin K.

Keep in mind that these vitamins help with many bodily functions and processes. They give you energy (vitamin B), help form your red blood cells (vitamin B & K), repair your tissues (vitamin C), and boost your immune system (vitamin C & A)! You cannot afford to ignore them.


  • The best way to avoid vitamin deficiencies is to eat natural whole foods! Filling your keto meal plan with high-nutrient foods like grass-fed steak, salmon, broccoli, spinach, cauliflower, free-range eggs, avocado, strawberries, raspberries, walnuts and almonds will ensure that you’re getting everything you need.
  • However, if you don’t have a lot of available natural low-carb options, consider taking vitamin supplements.

10. Disruption of Menstrual Cycles – uncommon

This is one of the worst keto side effects you can experience if you cut calories. The danger in missed periods is that it affects your fertility. It even increases your risk for osteoporosis, a condition where your bones become fragile.


  • Strict calorie counting is not necessary for keto. The concept of “calories in versus calories out” does not paint the whole picture. Protein and fats make you feel fuller, and you won’t even have to worry about overeating.
  • However, missed periods can also be a sign of a health problem unrelated to your diet. That’s why you should visit a doctor for a proper check-up!

Common Challenges on Keto

Cravings for High-Carb Foods

Let’s face it – cutting out high-carb foods can be tough. When you first start the keto diet, you may find yourself craving bread, pasta, and other carb-laden goodies. Managing these cravings is crucial to staying on track with your diet.


If you’re going to help curb those cravings you can try some Keto-friendly food swaps.

  • Bread alternatives: almond flour or coconut flour bread, lettuce wraps, or cauliflower crust
  • Pasta substitutes: spaghetti squash, zucchini noodles, or shirataki noodles
  • Snack options: nuts, seeds, cheese, or pork rinds

Difficulty in Meal Planning

It can be daunting to overhaul your regular grocery list and cooking habits, especially if you’re used to eating a high-carb diet. Instead, try diving into some meal planning resources.


  • Printable keto meal plans: Seek out online resources that offer weekly or monthly keto meal plans with accompanying shopping lists.
  • Recipe websites: Browse keto-specific recipe blogs or websites for meal inspiration and cooking tips.
  • Smartphone apps: Download a keto meal planning app to help you track your macros and find new recipes.

Social challenges

Dining out and attending social events can be difficult when following a keto diet. Navigating menus and finding keto-friendly options at restaurants or parties can sometimes feel like a Herculean task. To ensure you don’t falter on your keto progress, here are some tips to make dining out keto-friendly.


  • Research beforehand: Look up restaurant menus online to find keto-friendly options before dining out.
  • Customize your order: Don’t be afraid to ask for modifications, such as swapping fries for a side salad or requesting extra veggies instead of rice.
  • Chain restaurants: Seek out eateries with dedicated low-carb or keto menus to ensure you have plenty of choices.

Is Keto Right For You?

With all these side effects in mind, you might be wondering – is keto the right diet plan for me? Below is a list of questions to help you understand the diet better so you can make the best decision.

Who is keto best for?

Many people think that keto is only best for achieving weight loss. As it turns out, keto improves a person’s overall health.

It balances your blood sugar – great for patients with Type 2 Diabetes without kidney damage and anyone who is at risk for this medical condition.

Keto balances your hormones, regardless of your age. It can also reduce your risk of certain cancers.

Who is keto potentially dangerous for?

You need to know that keto isn’t for everyone. It is unsafe for those who are or have:

  • Pregnant women
  • Breastfeeding women
  • A medical condition (unless the person consults with a doctor first)
  • People who are trying to recover from a surgery
  • Those who have an eating disorder
  • Those who have problems with their liver and pancreas

My Recommendation

As a Registered Dietician, I advise anyone who wishes to embark on a low-carb journey to do a thorough research on the diet before trying it. Learn the basics of keto – how it works, benefits, its recommended macros, and how it differs from other diets.

I’ve heard stories of people who try keto and quit right away because of expected side effects. The problem was, they weren’t aware of those side effects and how to overcome them.

Some also experience worse on keto, all because they ate the wrong foods and failed to clear the diet with their doctor.

Health disclaimer

Whether you try keto or another diet, never leave a health professional out. If you can speak with a doctor who’s knowledgeable about low-carb diets and optimizing the diet based on your specific needs, do it.

Keto Diet FAQs

Here are some more questions about the ketogenic diet:

Is the keto diet safe long-term?

There are already studies (although not for all health conditions) that demonstrate that people can thrive on a properly formulated keto diet long-term.

For example, Virta Health trial patients with Type 2 Diabetes achieved healthy blood sugar levels and improvements in their cholesterol after 2 years of following the diet. Their weight and blood pressure also improved.

How much water should I drink on keto diet?

You need to consume at least 2.5 liters per day. This will help replenish the fluids you lose through your urine, especially at the start of the diet. But even if you’ve already adapted to keto, it’s still important to stay hydrated for overall health and longevity.

How long do keto side effects last?

Side effects of the keto diet, including keto flu, can last for a few days or longer. In extreme cases, they can last for a month. Over time, your body will adapt to using ketones for fuel, and you’ll feel better – even better than before you went keto!

What does keto diet do to your body?

The diet enables your body to burn through its stored carbohydrates and fat so that you can use ketones for fuel. Ketones are produced as your fat breaks down.

How do I know if I’m in ketosis?

Side effects such as keto breath, weight loss, and temporary fatigue tell you that the diet is starting to work.

But for accuracy, you need to check for the presence of ketones in your breath, urine, or blood. Such tests come in kits with indicators that you are in ketosis.

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