Breath Smells Like Nail Polish Remover?Keto, Fasting or DKA

If you’ve cut carbs or started fasting and someone mentions a sweet, fruity or nail-polish-remover smell on your breath, the likely cause is acetone. When your body burns more fat for fuel, it makes acetone, and because the molecule is small, some of it leaves on your breath.¹

How much acetone, and when

A 2015 review of breath acetone gives these levels, in parts per million (ppm):¹

Situation	Breath acetone
Healthy, not dieting	About 0.5 to 2 ppm1
Adults on a ketogenic (high-fat, low-carb) diet	Up to about 40 ppm1
Diabetic ketoacidosis (DKA)	Up to about 1,250 ppm1

What you eat moves the number most, followed by cutting calories, then exercise.¹

Long fasts add a second smell. In a study of 36 adults on supervised fasts of about 10 days, morning breath tests showed dimethyl sulfide rising during the fast, a sulfur gas tied to bad breath.² There was no comparison group, and three of the authors worked for the fasting clinic.² Fasting and crash dieting are on the standard list of bad-breath causes.³

Because this smell comes from your metabolism, a tongue scraper or mouthwash won’t change it much. Brushing and tongue cleaning still handle the mouth’s own share.³

The same smell, a different emergency

DKA happens when a lack of insulin lets ketones build up in the blood. Its symptoms include:⁴

• Thirst and peeing more often
• Stomach pain, nausea or vomiting
• Breathing more deeply than usual
• Fruity breath, like pear drops or nail polish remover
• Tiredness, sleepiness or confusion, and blurred vision

Symptoms usually build over 24 hours but can come faster.⁴ DKA can be the first sign of type 1 diabetes, particularly in children, so these symptoms are an emergency even if you’ve never been diagnosed with diabetes.⁴ Call 911 or have someone drive you; don’t drive yourself.⁴

If you take an SGLT2 inhibitor, a class of diabetes pills, DKA can happen without very high blood sugar. Doctors described 13 episodes in 9 people, and the normal-looking glucose delayed recognition by patients and providers alike.⁵ People on these pills who feel sick, vomit or feel unwell should be checked for ketones promptly.⁵ Ask your pharmacist whether your pill is in this class.

Reading your own breath

Fruity breath that started the week your diet changed, while you feel well, fits ordinary ketosis. Fruity breath with any of the symptoms above doesn’t. For other causes, see why your breath smells after brushing, morning breath and how to tell if your breath smells.

Try: “I started a low-carb diet two weeks ago and my breath smells fruity. I take a diabetes pill. Is it one of the kinds that can cause ketoacidosis, and should I test for ketones?”

Is It My Breath? covers this in Chapter 9, “Breath From Below,” in sections called “Fasting, Keto and Acetone” and “The Emergency Smell.” Its Breath Log has you write the day a new way of eating began at the top of the page, so you can see whether the smell started with it. See the book.