How to Tell if You’re in Weight-Loss Ketosis

Ketosis is not something you can just be ‘in’ or ‘out’ of. It comes in different degrees and these degrees have different effects on your body. Think of it as how strongly you’ve engaged your fat-burning engine. Daily, accurate measurements of your ketone levels provide an incredible insight into the way your body is responding to your diet — showing you exactly what certain foods or off-days do to your metabolism.

 Adapted from Stephen Phinney and Jeff Volek's  The Art and Science of Low-Carbohydrate Performance .

Adapted from Stephen Phinney and Jeff Volek's The Art and Science of Low-Carbohydrate Performance.

Understanding the Different Levels of Ketosis

There are three ketones that are byproducts of your body breaking down fat for energy. Their presence and saturation indicate your level of ketosis. Beta-hydroxybutyrate (BHB) is measured from blood; acetoacetate is measured from urine; and acetone is measured from breath. A ‘good’ level of ketosis depends on your weight-loss goals and your desired approach. The following values are for ketones measured by blood:

  • 0.5mmol/L of BHB is considered the low limit for ketosis. From here to 1.5mmol/L, weight loss begins — but won’t yet be optimal.

  • A reading in the range of 1.5–3.0mmol/L is optimal ketosis. This is the range for maximized fat burning, increased weight loss, and improved mental focus.

  • At blood ketone values greater than 3.0mmol/L, there are no added weight-loss benefits. For Type 1 diabetics, values between 3.0 and 8.0 mmol can be an early indication of ketoacidosis, a potentially lethal condition, and should prompt an immediate check in with your doctor. Read more about diabetic ketoacidosis here.

  • A blood ketone value greater than 8.0mmol/L cannot be achieved by a ketogenic diet and is a strong indicator of ketoacidosis. Symptoms include nausea, vomiting, abdominal pain, and confusion. Immediate medical care is required.

How to Measure Your Ketone Levels

We recommend using blood ketone meters — they are the only accurate way to measure your ketone levels. Despite what the packaging might say, readings from both urine strips and breathalyzers are only approximate and can be influenced by a number of factors. The amount of ketones in your urine or breath changes as your body becomes more and more keto adapted, but blood ketone meters retain their accuracy regardless of where you are in your keto journey.

Accuracy is important for several reasons:

  • You’ll know exactly how eating certain foods affects your ketone levels the next morning;

  • You’ll know exactly how long it takes to get back into ketosis;

  • And you’ll have a clear picture of your progress, giving you the motivation to keep your ketosis streak going.

If you have Type 1 Diabetes, accuracy also can provide you with early warning signs of ketoacidosis. We recommend meeting with your physician to make sure you are not suffering from Type 1 Diabetes if you are considering using urine strips or breathalyzers. Read more about diabetic ketoacidosis here.

Please note I have no financial or business relationship with any of the products I mention below.

Measuring Blood Ketones

Blood ketone meters give an accurate concentration of BHB down to the millimoles per liter (mmol/L). The measuring process is similar to measuring blood glucose: you prick your finger to draw blood and collect some on a strip. You then insert the strip into the meter, which reads out the results in a few seconds. The values below correspond with those listed on the graph above.

 

In millimoles per liter (mmol/L)

0.5–1.5 mmol/L = light to moderate weight-loss ketosis
1.5–3.0 mmol/l = strong weight-loss ketosis
3.0–8.0 mmol/L = therapeutic ketosis (epilepsy and cancer treatment)
8.0+ = potentially severe medical issues including ketoacidosis

 

The downsides of blood measurement are the cost and that it requires pricking your finger. Blood ketone starter kits like this one include a meter, a lancet, and blood strips. Most kits cost between $60–$100. The meter is a one-time purchase; blood strips by themselves cost about $1–$1.33 per strip ($30–$40 per month). I find the cheapest place to buy them is on Amazon or eBay — just be sure to check the expiration date before you purchase. The lancet you’ll use to prick your finger will need to be replaced when it becomes dull.

Measuring Urine Ketones

Urine strips are the cheapest way to measure ketosis. Unfortunately, they do not provide an accurate reading of your ketone levels. Measurements don’t involve exact numbers, but instead matching the color of the strips to a key on the box. Also, ketone levels in urine are affected by several factors. How much you drink will impact the concentration of ketones (though this can be helped somewhat by keeping your daily intake of fluids consistent). Also, as the months go by and your body more effectively utilizes ketones, smaller amounts of them will end up in your urine.

While you cannot get an accurate reading, urine strips can help you gauge your relative level of ketosis — are you in stronger ketosis today that you were yesterday? If you are struggling to lose weight in ketosis or are nearing the end of your weight-loss journey, switching to blood meters will give you the added accuracy you need.

To use a urine strip, hold the strip in your urine stream for a few seconds. Within 10–15 seconds, you’ll notice a color change in the strip if you are in ketosis. At that time, match the strip color with the color code on the box or vial for the ketone amount. Waiting too long to read your strip can result in further inaccuracy as the color will continue to darken. Research shows that testing is best done in the early morning or several hours after dinner.

Measuring Breath Ketones

While it is the most simple and least invasive test, we do not accept breath ketone meter readings because we do not have thorough data on their accuracy. We are currently executing our own tests and may be able to accept them in the future.