Evidence Based Nutritional Ketosis

Keto Breath: A Complete Guide

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The ketogenic — or “keto” — diet is gaining popularity around the globe. Many people have found that following the keto diet is an effective, efficient way to reduce body fat. Plus, there are numerous other health benefits of the keto diet, including lower insulin levels and increased mental energy. 

Specifically, the keto diet consists of a low intake of carbohydrates, paired with a high intake of fats and proteins. The objective of the keto diet is to lead the body into a state of “ketosis.” Ketosis occurs when your body breaks down stored fat for energy, because the typical energy source (carbohydrates) is not available. As a result, the liver releases higher amounts of ketones into the bloodstream. 

While there are many positive side effects of the keto diet, there are also some that we could do without…namely, keto breath. Unlike most cases of bad breath that can be solved by simply brushing and flossing, keto breath can be somewhat harder to beat. 

But, don’t worry. Keto breath is no reason to throw in the towel and down a barrel full of carbs. In this article, we’ll run through the most common causes of keto breath, and what you can do to keep your mouth smelling fresh. 

Do You Have Keto Breath?

If you’re on the keto diet and are beginning to feel self-conscious about opening your mouth ever again, don’t worry. If you haven’t noticed a change in your mouth or breath, then you likely don’t have keto breath. In fact, some people on the ketogenic diet never experience keto breath. For those who do, keto breath usually only lasts for a couple of weeks as their body adjusts to this new diet.

According to most people who have experienced keto breath, the condition is very obvious. 

Keto breath isn’t like an ol’ case of bad breath. It has a unique taste and smell. This will — of course — vary based on your body chemistry and specific diet. Some people describe keto breath as a strong, sharp, fruity odor. Others claim that their keto breath smells more like nail polish remover. Still, others say that they knew they were in ketosis when they began experiencing a distinct metallic taste in the back of their mouths. 

If any of the above scents and sensations sound familiar, then you’re probably experiencing keto breath. Keep reading to learn about specific causes of keto breath, and what you can do to fight it.

Common Causes of Keto Breath

We know that eating a keto diet causes keto breath, but what exactly occurs within your body to affect your breath? 

The three main causes of keto breath are acetone, ammonia, and dehydration. Now let’s look at each of these causes in detail. 

Acetone is one of the primary ketones produced by your liver. You see, when your body enters ketosis, extra ketones need to leave your body. 

On the Standard American Diet, the average person consumes nearly 300 grams of carbs per day. On a ketogenic diet, you typically consume less than 25 grams of carbs per day. As a result, your body changes the way it metabolizes energy.

Rather than looking to carbs for energy, your body begins burning fat. And, when your body breaks down fat as an energy source, your liver produces ketones.

In addition to acetone, your liver also produces ketones such as acetoacetate and beta-hydroxybutyrate. 

Bear in mind, your liver produces ketones even when you’re consuming a carb-based diet…just not nearly as many.

As a result of ketosis, your body has more ketones than it can use. When you have excess ketones, they are removed from your body via your urine and your breath.

When ketones are removed from your breath, they circulate through your blood and pass through the air in your lungs. Typically, this interaction with air is what results in the strong smell that escapes in your breath.  

You see, acetone is one of the most prominent ingredients in nail polish remover, so this can cause a strong chemical-esque, sweet odor in your breath.

Ammonia is another common cause of keto breath. Ammonia is not a ketone, but it is produced when your body breaks down protein.

In the Standard American Diet, people obtain their calories in the following percentages: 

  • 35% fat
  • 15% protein
  • 50% carbohydrates

When you’re following the standard ketogenic diet, you obtain your calories in the following percentages: 

  • 70-80% fat
  • 20-25% protein
  • 5-10% carbohydrates

If you compare these percentages, the keto diet already has you consuming more protein than you probably would by following a Standard American Diet. 

Therefore, your body is producing more ammonia than usual.

However, many keto newbies eat too much protein instead of eating more fat.

If you take in more protein than your body can use, the excess ammonia produced in protein digestion needs to exit your body. Similar to ketones, these excess molecules are dispelled in your urine and your breath.

If the word “ammonia” seems familiar, it’s because you’ve likely seen this chemical listed as an ingredient in cleaning products (like glass cleaners and degreasers). The smell of ammonia is very potent and sharp — in fact, ammonia is so powerful it’s not even recommended  for inhalation. 

If you’re suffering from keto breath, then you want to check your protein levels and make sure you’re consuming the right percentages of carbs, fats, and proteins. Additionally, women don’t require as much protein as men, so bear this in mind when selecting foods. Furthermore, if you don’t lead an active lifestyle, then you may also consider lowering your protein intake. 

This brings us to the final common cause of keto breath: dehydration. A diet low in carbs can cause dehydration. Scientifically speaking, dehydration is when you consume less water and fluids than your body needs. 

On a Standard American Diet that is rich in carbs, your body stores excess glucose as glycogen reserves in both your liver and muscles. When your body runs low on glucose for energy, your cells turn to these glycogen reserves for fuel. For every gram of stored glycogen in your body, there are three or four grams of attached water. 

(Sidenote: this is why keto causes you to lose so much water weight. Your body runs through these glycogen stores rather quickly, before resorting to fat as an energy source.)

When you’re in ketosis, your body doesn’t have an alternative method for retaining excess water. This is why you need to remember to consistently drink water throughout your day. It’s incredibly common for keto dieters to experience dehydration, as they are not used to being mindful about their fluid intake. In a Standard American Diet, your body can obtain a lot of the water it needs from food.

When you don’t have enough water, you become dehydrated. The symptoms of dehydration while in ketosis are: 

  • Diarrhea
  • Vomiting
  • Increased thirst or craving for liquids
  • Keto headache (also a common symptom of adjusting to ketosis)
  • Keto flu (also a common symptom of adjusting to ketosis)
  • Dizziness
  • Inability to retain focus
  • Fatigue
  • Dark-colored urine
  • Dry skin
  • Dry mouth

Obviously, dry mouth is at the lower end of severity in this range of side effects, but for the sake of this article, this is where we will keep our focus. After all, we’re only concerned with understanding and treating keto breath. 

So, when your mouth is dry, it produces less saliva. Saliva is responsible for rinsing your mouth of odor-causing bacteria.

Without saliva to eliminate these smelly bacteria, their bacterial colonies grow. At the same time, when you don’t drink enough water to flush out all your extra ketones, these ketones accumulate and hang out in your mouth.

The result is doubly-bad breath, caused by both ketones and bacteria. Ick. Make sure you’re drinking plenty of water. 

How to Stop Keto Breath in its Tracks

Bad breath is no reason for you to throw in the towel and quit your keto diet. After all, keto breath typically only lasts for a couple of weeks as your body adjusts to being in ketosis. Hang in there, and your breath should return to normal soon!

But, in the meantime, here are some tips for you to keep your breath smelling fresh as a spring flower.

#1: Stay Hydrated

Staying hydrated not only flushes odor-causing bacteria from your mouth, but it also increases the likelihood that your excess ketones will exit via your urine, rather than through your mouth. If you can get your ketones to flush through your urinary tract, then this equals fresher breath for you. 

Start carrying a water bottle with you wherever you go. You can even add fresh lemon to your water — lemon is a natural breath freshener, and it helps to kill some of the bad bacteria that may be lingering in your mouth. 

#2: Rethink Your Oral Hygiene

If your keto breath is really bugging you, then you can also fight this by boosting your oral hygiene practices. This may seem obvious, but sometimes the most obvious solutions are the best. Start bringing a travel toothbrush and toothpaste with you to work, and brush after snacks and meals. 

Additionally, you can purchase a special mouth rinse to fight keto breath. As the ketosis adjustment period sometimes results in dry mouth and overall dehydration, you can purchase a mouth rinse with chemicals that help to keep your mouth moisturized. For instance, check out this specialized mouth rinse from Biotene

#3: Check Your Macros

If you’ve been on your keto diet for a while now and you can’t seem to shake keto breath, then this may be a sign that you need to recalculate your macros. If you’ve just lost a significant amount of weight, or if you’ve made changes to your fitness routine, then you’re going to need to adjust your diet. Otherwise, these changes could throw your body off-balance and result in excess ketones or ammonia in your breath. 

Use an online Keto Macro calculator (such as this one) to make sure you’re eating the right percentages of fat, protein, and carbs for your weight, activity level, and gender. 

Additionally, you can try experimenting with your diet by slightly decreasing your protein intake, or slightly increasing your carbohydrates intake. After each adjustment, monitor your body for a few days and see if you notice any changes in your breath.

Following a keto diet is not set in stone — you will need to constantly make adjustments based on your body and lifestyle. Check in with your body — if you feel a lack of energy, or if feel like something isn’t quite right, then there are steps you can take to tailor your diet to your needs.

#4: Try Natural Breath Fresheners

Before you reach for a pack of mint gum, read the label. Most gums and breath mints contain sugar or sugar substitutes — both of which can throw you off your keto game. Unless you calculate gum and breath mints into your keto diet, you’re probably better off using a natural breath freshener. 

Trying chewing fresh mint leaves if you need a quick breath freshener. You can find whole mint leaves in the produce and herb section of your supermarket (or, you can even grow your own!). Cinnamon, parsley, and rosemary are also good options if you aren’t a huge fan of mint.

If you’re really into DIY, then you can even make your own natural mouthwash by combining essential oils, vinegar, and distilled water. It’s super easy to find a recipe online. You can keep your new homemade mouthwash in a mason jar, or pour it into a spray bottle to freshen your breath on the go!

How To Track Your Ketones

Well, there you have it. Now you know all about keto breath, how it happens, and how you can stop it. Don’t give up on your keto diet, just because of some bad breath!

Altering your diet in such a drastic way is naturally going to have some side effects – but you can easily power through this initial discomfort and achieve your weight goals.

Tracking your ketones is a vital part of the weight loss process. Because we were sick of cheap, inaccurate devices, we invented the first and only clinically-backed ketone breath monitor. The monitor is accurate enough to replace invasive blood measurements.

By simply breathing into our device, you will have a reliable measurement of your current ketone levels in seconds. You will know your fat burning levels instantly, and be able to effectively track your fat loss. No more urine strips, no more pricking your finger – just a fast, easy and reliable breath test.

You can bring our device with you to the office, take it to the gym – you can truly check your ketones anywhere. Unlike previous devices, which were often poorly made, unreliable, and not backed by clinical research – our ketone breath monitor is patented.

This means no other device is legally allowed to use our exclusive technology. Whether you are brand new to keto and want a convenient and reliable way to check your ketone levels and monitor your fat loss, or you’re an elite level biohacker – we are the perfect way to measure your ketones.

You don’t need to worry about continually buying strips, continually pricking your finger – we have all you need, in just one device. One of our favorite features is the personalized insights you get with the device. Every time you measure, your results are graphed and stored, so you can easily track your progress and fat loss and share with clinicians, coaches, or friends.. 

Until now, there has not been an easy and convenient way to check your ketone levels – which has made many people give up on keto entirely. But that outcome is no longer necessary, as we’ve made a device that does all the work for you.

Just simply take one breath into the device, and within seconds you’ll know your ketone level. Whether your goal is to measure fat loss , lose weight, improve your blood sugar – we have the answer.


Casey Thaler, NASM-CPT, FNS

Casey is one of the most highly-regarded voices in the paleo and keto communities. He has written over 200 articles on health, science, nutrition, and fitness. As a National Academy of Sports Medicine certified personal trainer and fitness nutrition specialist, he has also helped thousands of people lose weight, look younger, and live their healthiest lives. He is also the author of the best-selling title, The Essential Instant Pot Keto Cookbook.

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