Eating a carb-restricted diet reduces the amount of carbs that our body stores for energy. When our carb stores are depleted, our body will begin searching for other sources of fuel and start converting fat into ketones.

Like intermittent fasting, exercise can speed up our body's process of burning carb stores. This triggers the body to start producing ketones for energy.

Like carb-restricted diets, intermittent fasting depletes our carb stores over time. During fasting periods, our body uses stored carbs for energy until they are depleted and switches to ketone production.

Blood tests use a handheld device and test strips to measure BHB, the primary ketone body that your body actually uses for fuel. Urine and breath tests measure other types of ketone bodies. As a result, blood tests are the most accurate way to measure meaningful ketone levels.

Breath tests use a special meter to measure acetone levels, a ketone body excreted through the breath. Breath tests measure acetone, a waste product, instead of BHB, the main ketone body used for fuel. As a result, they are not as accurate as blood tests. Food and drinks like gum, coffee, and garlic could also impact test results.

Urine tests use strips that change color based on AcAc concentration in your urine. AcAc is a ketone body found in the urine as well as the blood, although at lower levels than BHB. Urine tests become less accurate over time. As your body becomes more efficient at converting ketones into fuel, you will begin excreting less and less AcAc in your urine.