You’ve started on the keto diet and noticed something’s off…

You can taste a metallic, unappetizing taste in your mouth that wasn’t there before. This unpleasant but totally temporary new taste is known as “keto breath.”

While the keto diet has been shown to induce a variety of great health benefits, don’t be too surprised if you start experiencing some pesky side effects—like keto breath—in the beginning.

Don’t worry, though. It’s just your body adjusting to the changes that come from altering your diet so drastically.

In this article, we’re going to review what keto breath is and how you can overcome it as quickly as possible!

What Causes Keto Breath

During the first week or two of the keto diet, your body is going to go through some adjustments as you lower your carb intake and rely more on healthy fats for energy.

These changes may range from disrupted sleep to experiencing the “keto flu”, which can encompass everything from nausea to dizziness.

The keto diet is based on changes your body makes when switching to being predominantly “sugar-burning” metabolism to “fat-burning” metabolism.

After reducing your carbohydrate intake sharply, your body will eventually use up all of the stored glycogen for energy.

Consequently, the body breaks down the fat you eat on keto for energy and produces ketones (the process is known as ketogenesis).

Once your body is in a state of ketosis, your body produces less hunger signaling hormones, which means less calories consumed per day because of greater satiety.[1]

Ketones are natural chemicals your body produces during this process. These ketones are acetone, beta hydroxybutyrate, and acetoacetate. Acetone is thought to be the main culprit behind keto breath and is a pretty reliable indicator that you’re in ketosis.[2]

You can measure your breath acetone levels by using an inexpensive ketone breathalyzer (generally available at pharmacies and online).

Acetone is actually one of the main ingredients found in nail polish remover, so when your breath starts to smell or taste like nail polish remover, it could be an indicator that ketosis is occuring.

Though it’s a good thing when you’re entering ketosis—since it shows the keto diet is working—it’s not such a good thing to harbor a bad-tasting smell/taste in your mouth. Clinically, “bad breath” is known as halitosis, and it can be a sign of poor oral hygiene.[3]

Not only is foul-smelling breath socially embarrassing, but it can even lead to complications with your interpersonal relationships as well as avoidance behaviors, depression, and anxiety.[3]

One study examined the emotional effects of bad breath, citing that the National Dental Association reported that 50% of the adult population has suffered from an occasional malodor disorder, and 25% have been reported to have a chronic problem.[4]

Obviously, external factors contribute to bad breath too, such as alcohol consumption, smoking, and poor oral hygiene. Internal factors ranged from liver diseases to gastrointestinal issues.

Another situational cause was dental anxiety or fear of going to the dentist. This can lead to patients avoiding visits and treatments.

The biggest emotional aftereffect of bad breath was social anxiety.

Ways to Counteract the Effects of Bad Keto Breath

There are ways to beat keto breath and halitosis, so hang in there!

The following suggestions will not only improve your breath but also your overall oral hygiene.

Drink More Water

Halitosis and keto breath are amplified when your mouth is dry and dehydrated. Hence, drinking water is imperative for reducing the smell of keto breath as well as supporting ketone excretion. The more water you drink, the faster your body will flush out ketones.

Use a Long-Lasting Mouthwash Before Bed and After Waking

There are many mouthwash products available that are designed to combat bad breath for extended times, such as Smart Mouth and Biotene. They tend to be a little pricier but if you’re experiencing chronic keto breath, the investment is well worth it. In most cases, you will only need to rinse once or twice per day for lasting results. The advantage of these is that the effects are immediate and you can go about your day not having to stress about how your breath smells.

Brush and Floss Your Teeth After Meals

It should really go without saying that maintaining proper oral hygiene is the most effective way to defend against keto breath. Make sure you’re brushing and flossing at least twice per day, if not three times! Also, consider tongue scrapers and zinc-based toothpaste.

Chew Gum and/or Use Breath Spray Throughout the Day

Chewing gum can be a practical and easy way to eliminate foul breath odors, especially after eating. However, be wary that many gum products are packed with added sugars and artificial sweeteners. The best gum for keto is Spry which is a non-caloric gum naturally sweetened with xylitol (sugar alcohol). Spry is specifically made to target oral hygiene and treat bad breath. PUR Gum is also keto-friendly since it has no artificial sweeteners like aspartame.

Slightly Reduce Your Protein Intake

The keto diet only requires moderate protein consumption, not necessarily high consumption. Eating excessive amounts of protein can cause volatile sulfur compounds to buildup in the body and mouth, leading to burping (and gas) that smell foul. If you notice you belch and pass gas a lot, it might be prudent to reduce your protein intake a bit and see how your symptoms change.


While keto breath is a good indicator that you’re in ketosis, it is an unpleasant and nerve-wracking side effect of the keto diet.

Just hang in there and know that this is only a temporary side effect as your body adjusts to the ketogenic lifestyle.

After all, the keto diet has can help improve health in many ways, especially by promoting weight loss.

In the meantime, start making some minor adjustments and pay more attention to your oral hygiene routine to kick that keto breath to the curb!


[1] Gibson, A. A., Seimon, R. V., Lee, C. M., Ayre, J., Franklin, J., Markovic, T. P., … & Sainsbury, A. (2015). Do ketogenic diets really suppress appetite? A systematic review and meta‐analysis. Obesity Reviews16(1), 64-76.

[2] Musa-Veloso K, Likhodii SS, Cunnane SC. Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals. Am J Clin Nutr. 2002 Jul;76(1):65-70.

[3] Thoppay, J. R., Filippi, A., Ciarrocca, K., Greenman, J., & De Rossi, S. S. (2019). Halitosis. Contemporary Oral Medicine: A Comprehensive Approach to Clinical Practice, 1719-1747.

[4] Settineri S, Mento C, Gugliotta SC, Saitta A, Terranova A, Trimarchi G, Mallamace D. Self-reported halitosis and emotional state: impact on oral conditions and treatments. Health Qual Life Outcomes. 2010 Mar 26;8:34. doi: 10.1186/1477-7525-8-34.