Do Ketones Mean You're Burning Fat?

Normally, your body uses carbohydrates as a preferred source of energy. However, when the number of stored carbohydrates in your body (stored glycogen in your liver) decreases, this forces your body to turn to using stored fat for fuel

During ketosis, your liver breaks down fats into substances called ketones, which are byproducts of fat metabolism. Ketosis can be achieved by fasting, switching to a low-carb diet, or following a ketogenic (keto) diet (low-carb, high-fat). Combining a keto diet and exercise helps you reach ketosis faster.

When your body is in ketosis, it is burning fat at such high rates that ketones can be detected in your blood, urine, or breath. And the level of ketones indicates the amount of fat being burned. However, to reap the benefits of ketosis without the harmful side effects, ketone levels should still be less than 3 mg/dL.

You can measure your ketone levels during ketosis in one of three ways:

1. Urine ketone strips: Urine ketone strips are relatively inexpensive and can give you a rough idea of ketone levels in your body, although results may be slightly inaccurate.
2. Blood ketone tests: Blood ketone tests are the most accurate and most expensive way of measuring your ketone levels. They are performed using a kind of blood glucose meter that also helps test for ketones. 
3. Breathalyzer: A breathalyzer can detect ketones in your breath. Results are less accurate than blood ketone tests but more accurate than urine ketone strips. While the initial cost of a breathalyzer device is pretty high, it’s still a one-time investment that allows you to check your ketone levels frequently without worrying about additional costs each time you want to do a test.

In order to determine what ketone levels are optimal for each type of test, speak to your doctor.

To achieve ketosis, you need to lower your carb intake to less than 50 grams per day. It usually takes about 4-12 weeks to adapt to a keto diet, during which time you may experience what some call “keto flu”—a group of symptoms that may appear as your body adjusts. Symptoms of keto flu include

• nausea,
• fatigue,
• dizziness, and
• bad breath.

Drinking plenty of water can help ease or keep some of these symptoms at bay.

Ketone levels higher than 10 mg/dL are dangerous. If you are on a keto diet and feel extreme symptoms of keto flu, you need to keep measuring ketone levels in your body at regular intervals to ensure that they aren’t too high. This is particularly important if you have diabetes or consume a lot of alcohol.

• High ketone levels can lead to a life-threatening condition called ketoacidosis.

Following an aggressive keto diet can also cause dehydration and electrolyte imbalances. If you have conditions such as kidney disease, liver disease, or diabetes, ask your doctor before starting a keto diet.