What causes sweet or fruity breath?

If your breath suddenly smells sweet or fruity, don't brush it off. It can happen when the body makes ketones, such as during a keto diet, but a clear fruity smell can also warn of diabetic ketoacidosis (DKA), a dangerous diabetes complication. Dry mouth and dental problems can cause bad breath too, though that odor may not be truly fruity. If the change is sudden or you feel sick, it is important to know what to do next. 

What you will learn in this article: 

• A keto diet can raise breath acetone and give breath a sweet smell. 

• Fruity breath can be a sign of DKA, which needs emergency medical care. 

• Dry mouth, plaque, gum disease and cavities can cause common bad breath. 

• A dentist can check for mouth-related causes, but possible DKA needs medical care. 

If you've noticed an odd sweet or fruity smell on your breath, schedule an appointment with an Aspen Dental provider. Your care team can check your mouth for common causes and help you figure out next steps. 

Why does breath smell sweet or fruity? 

A few things can change the way your breath smells. Some causes begin in the mouth. Others happen when the body breaks down fat and makes ketones. 

Low-carb or keto diets 

When you eat very few carbs, your body may burn more fat for fuel and make ketones. One of those ketones is acetone, which can leave the body in your breath and create a sweet smell. In a small study published in The American Journal of Clinical Nutrition, breath acetone rose in 12 healthy adults after they ate ketogenic meals.¹ Because the study was small and short, it does not show that everyone on a keto diet will notice this change. 

A sweet smell during a keto diet does not by itself mean you have DKA. Still, do not assume the smell is only from your diet if you have diabetes or feel sick. 

Dry mouth 

A dry mouth can add to regular bad breath. MedlinePlus lists dry mouth, mouth bacteria, gum disease and cavities as possible causes of bad breath.² This does not mean a clear fruity odor is harmless. 

Bacteria on your tongue and teeth 

Poor brushing and flossing can let bacteria build up in your mouth and between your teeth. Those bacteria can make breath smell bad. Brushing, flossing and cleaning your tongue each day may help with this type of odor. 

Diabetic ketoacidosis 

DKA is the most serious cause discussed in this article. It can be life-threatening. It happens when the body does not have enough insulin to let blood sugar enter cells for energy. The liver then breaks down fat and makes ketones. If too many ketones form too fast, they can reach dangerous levels. 

The Centers for Disease Control and Prevention lists fruity breath, dry mouth, fast or deep breathing, feeling very tired, nausea, vomiting and stomach pain as signs of DKA. It can also be the first clear sign of diabetes.³ 

When is fruity breath a medical emergency? 

Do not assume fruity breath is only a mouth problem. Get emergency help now—call 911 or have someone take you to an emergency room—if any of these apply:³ 

• Your breath smells fruity. 

• Your blood sugar stays at 300 mg/dL or higher. 

• You are vomiting and cannot keep food or drinks down. 

• You are having trouble breathing. 

• You have several signs of DKA at the same time. 

Do not wait for a dental visit or try to cover the smell with mouthwash. 

Could it be a dental problem instead? 

Sometimes what seems sweet is common mouth odor. Dry mouth, plaque bacteria, gum disease and cavities can all play a part. A dentist can check your teeth, gums and tongue for a mouth-related cause. They can also tell you when the problem may need a doctor’s care instead. 

If the odor is clearly fruity or you have any of the warning signs above, get emergency medical care first. 

What should you do about it? 

Start by deciding whether this could be an emergency. If your breath smells clearly fruity, follow the emergency steps above. This is even more urgent if you have diabetes or feel sick. 

For common mouth odor without emergency warning signs, brush and floss your teeth, clean your tongue and drink water. If the odor lasts, see your dental provider. They can check for dry mouth, gum disease, cavities or another dental problem. If they do not find a dental cause, contact a doctor. 

For ongoing bad breath without emergency signs, contact your local dental provider. They can check for dental causes and help you plan the next step. 

What causes sweet or fruity breath? FAQs 

Still have questions about fruity breath? These answers cover a few common concerns. 

Can fruity breath happen without diabetes? 

Yes. A keto diet can raise breath acetone and cause a sweet odor without diabetes being involved. But a fruity smell is also a DKA warning sign, and DKA can be the first sign of diabetes in someone who hasn't been diagnosed yet. Don't rely on smell alone to rule DKA out. Follow the emergency advice above if you notice it. 

How fast can diabetic ketoacidosis get serious? 

DKA often begins slowly, but more serious symptoms can appear fast. If you notice fruity breath or other DKA signs, call 911 or go to an emergency room. 

Should I see a dental provider or a doctor first? 

Get emergency medical care first if your breath smells fruity or you have DKA warning signs. For ordinary bad breath without emergency signs, a dental provider can check for mouth-related causes. A doctor can check for medical causes. 

Can brushing and mouthwash fix fruity breath? 

Brushing, flossing and mouthwash may freshen common bad breath. They will not treat DKA or another medical cause. If the smell stays, get the cause checked instead of trying to cover it. 

Sources 

¹ National Institutes of Health, National Library of Medicine, The American Journal of Clinical Nutrition: “Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals.” https://pubmed.ncbi.nlm.nih.gov/12081817/ 

² National Library of Medicine, MedlinePlus: “Bad Breath.” https://medlineplus.gov/badbreath.html 

³ Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Diabetes: “Diabetic Ketoacidosis.” https://www.cdc.gov/diabetes/about/diabetic-ketoacidosis.html