Admit it. You've had bad breath at one time or another, particularly upon waking. But if that foul smell lingers even after you've tried to brush it away, you might want to consult a doctor.

Turns out that your breath can be one of the telltale signs that something is wrong with your body.

For years doctors have been able to link certain breath odors with different medical conditions. Now they are beginning to use tests that can diagnose a particular disease by a person's breath alone, Medical Daily reported.

Scientists are using mass spectrometers that can detect the minute amounts of chemical compounds in your breath to help identify what may be going into your body, according to The Wall Street Journal.

"Anything you can have a blood test for, there is potentially a breath test for, as long as there is a volatile component," said Raed A. Dweik, director of the pulmonary vascular program at the Cleveland Clinic's Lerner Research Institute, in an interview with The Wall Street Journal.

In most cases, bad breath is caused by bacteria that sit at the back of your tongue, throat, and tonsils, Harold Katz — founder of The California Breath Clinics — told the Daily Mail in a video interview. The bacteria in these areas produce volatile compounds that give your breath its bad odor.

Sometimes these volatile compounds carry distinct smells that indicate key things about your health.

1. Diseases

Certain diseases such as diabetes, kidney failure, and lung cancer can be detected in your breath, according to Everyday Health

If you have an untreated or poorly treated case of diabetes, your breath may have a fruity smell, otherwise known as acetone breath. Acetone breath can indicate a serious problem in diabetic patients called ketoacidosis. That's when the body doesn't have enough sugar to use for energy and it consumes fatty acids as a substitute. When these fatty acids break down, waste products called ketones build up in the body, according to Medical Daily. This condition can ultimately result in a diabetic coma or even death.

Signs of kidney failure can also be detected in your breath. If you have chronic kidney failure, your breath will have a pungent, fishy odor or smell like ammonia, according to the U.S. National Library of Medicine.

2. Tooth Decay

Tooth decay is one of the primary causes of bad breath, according to Katz. It happens when a bacterium called Streptococcus mutans produces acids that destroy your tooth enamel. This slow deterioration of your tooth and what's happening below your tooth's surface is what really stinks.

When plaque and tartar build up on your teeth and aren't removed, you might experience a condition called periodontitis. That's when bacteria attach themselves to your teeth and gums and create an infection. If not treated, small pockets can form between your teeth and gums, which can result in bad breath and, at the worst, cause your teeth to fall out.

3. Sleep disorders

When you sleep, your saliva production dramatically drops. Because of this, odor-causing bacteria have a chance to grow and form in your mouth undisturbed. If you have a sleep disorder, especially sleep apnea, you are more prone to this happening.

Sleep apnea is a condition in which you experience on-and-off disruptions in your breathing while you sleep. With this condition, you're more likely to breathe through your mouth, which can affect saliva production and cause bad breath. If you have sleep apnea, your breath will be sour, according to Everyday Health.