How to Detect Ketosis

The state of ketosis, how to check your ketones and read ketone strips

How can you tell if your low-carbing efforts have been effective enough to induce ketosis? Learn how to check your ketones!

The state of ketosis

The state of ketosis means that the body has switched from depending on carbohydrates for energy to burning fats for fuel. This means not only dietary fats (olive oil, guacamole, deep-fried pig ears), but also all the jiggly bits around your waist — clearly a desirable state for anyone looking to shed extra weight.

When the body metabolizes fat, it generates molecules called ketones (also known as ketone bodies). As you restrict carbohydrate intake and amp up the dietary fat, more fat is metabolized and a greater quantity of ketones are created. Most of the cells in your body — including those in your brain — are able to use ketones for energy, although many people experience a few days’ adjustment period, often called the low carb flu.


One of the varieties of ketones generated — acetone — cannot be used by the body and is excreted as waste, mostly in the urine and the breath. Conveniently, this makes it very simple to measure whether or not you are in ketosis.


Upon entering ketosis, some people report a distinct change in the smell of their breath as a result of the extra released acetone. It could be “fruity” — it’s been likened to overripe apples — or even “metallic.” If you notice this happening during your first few days of changing your diet, it could be a good sign you’re in ketosis.

The unusual smell isn’t anything dangerous, but it could be annoying. Drinking plenty of water should help, or get yourself some sugar-free gum. Most people report “keto-breath” diminishing after the first few weeks.

Detecting ketones in urine

The more accurate way — and the one we recommend — to check for ketosis is by using ketone urine testing strips, often referred to by the brand name Ketostix. These inexpensive testing strips are the perfect solution for instantly checking ketone levels in your urine.

Pass the test end of the small paper strip directly through your urine stream (alternatively, collect urine in a clean, dry container and dip the strip in afterwards). Shake off any excess, then wait 15 seconds. If you’re in ketosis, the strip will change color from its original beige — compare the color to the guide on the side of the bottle to find out how “deep” your level of ketosis is.

Deeper purples generally indicate higher levels of ketones. Don’t take this to mean that darker is necessarily better – plenty of people find low-to-mid level ketosis to be a “sweet spot” for linear fat loss and muscle gain while feeling energized.

how to read ketone strips

Potential errors from testing for ketones in urine

Ketone levels in the urine don’t necessarily match ketone levels in the blood. There are a couple reasons why this might be the case.

How hydrated you are can make a big difference regarding the concentration of ketones in your urine. Dehydration may result in a false positive, which some folks find happens every morning to a mild degree. Likewise, drinking a ton of fluids — and you should be drinking water like it’s your job — will result in a lower concentration of ketones, meaning a false negative.

As time goes on, people following ketogenic diets tend to measure lower levels of ketones in their urine despite still being solidly in fat burning mode. At this point, a blood test may be necessary to accurately test for ketosis — but these are significantly more expensive (plus, you have to prick your finger instead of simply urinate). If you’ve been following good eating habits and have been consistently in ketosis for the weeks following, there’s likely no need to fret over it.

The bottom line

  • Being in ketosis generates elevated levels of ketones, which are detectable in the breath, urine, and blood.
  • Ketone urine testing strips (like Ketostix) are the quickest, easiest way to test for ketones in urine.
  • Hydration and amount of time spent in ketosis may affect Ketostix results.
  • Ways of how to check your ketones include ketone urnite testing strips or a change of your breath smell also known as keto-breath