Ketones in Urine

Molecules your body makes when it burns fat for fuel.

Ketones are what your body produces when it runs on fat instead of carbohydrates. For someone on a low-carb or ketogenic plan, seeing them is the point. For someone with diabetes, high ketones are a warning sign that needs attention. Same molecule, very different meaning — context is everything.

What ketones are

When carbohydrate intake drops — through fasting, a ketogenic diet, or prolonged exercise — the liver converts fat into ketones to fuel the body and brain. Excess ketones leave through urine, which is what a test strip picks up.

Why levels change

Diet is the biggest lever: the fewer carbs you eat, the more ketones you’ll typically produce. Exercise, illness, and pregnancy also move levels. In diabetes, ketones can rise dangerously when the body lacks insulin — especially alongside high blood sugar — a condition called diabetic ketoacidosis that needs urgent medical care.

What a result can tell you

If you’re following a ketogenic plan, urine ketones confirm you’ve shifted into fat-burning and help you see how food choices affect it. If you have diabetes, a ketone check during illness or unexplained high glucose gives you an early warning — and a reason to contact your care team promptly if levels are moderate or high.

What it can’t tell you

Urine ketones lag behind blood levels by a few hours, and hydration dilutes or concentrates the reading. Long-term keto adapters may also excrete fewer ketones despite being in ketosis. If you have diabetes and readings are climbing, don’t interpret alone — that’s a call to your provider.