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Checking for Ketones

Checking for ketones

By Beth Zupec-Kania, RDN, CD

A frequently asked question when starting a ketogenic diet therapy is “how do I know I’m in ketosis?”. There are three different methods for checking and monitoring ketosis. I’ll explain each then give examples of how my patients have selected the one to best suit their needs.

Urine ketones (acetoacetate); the simplest and cheapest but least accurate of all methods. This method may be “good enough” for most people who are monitoring themselves at home and are able to get a more specific level at their doctor’s office. The reason that urine ketones are not precise it measures the ketone called acetone that is cleaned out of the blood by the kidneys. Another reason is that the amount of liquid that you drink can change the reading. If you are drinking very little an hour before you check, the urine ketone reading can appear strong on the urine test-stick because they are concentrated. If you are drinking a lot before you check, the ketones can appear weak because they are diluted.

Example: I’m working with a  5-year-old who started on  ketogenic diet therapy over a year ago for epilepsy. Our plan was to start with the simplest method of checking ketones and if needed, we’d graduate to another method during “fine-tuning” of his diet to achieve better seizure control. After three months on the diet his seizures stopped completely, no diet changes were needed and so there was no reason to change to another method of checking ketones.

Products: there are only a few different companies that make urine ketone test strips. The One Earth Health brand is the most reasonably priced. My patients like the color chart on the bottle which shows an estimate of the blood ketone betahydroxybutrate along with the urine reading.

Blood ketones (betahydroxybutryate); this method has an advantage over urine ketones in that it reveals ketosis in real time and is not affected by the amount of liquid that you drink. The betahydroxybutryate (or BOHB for short) level also correlates to blood glucose which can be helpful in adjusting the diet. The lower the blood glucose, the higher the BOHB level. For this reason most of my patients prefer to check both levels simultaneously. If you are taking exogenous ketones of salts or esters that are primarily the L-BOHB version which the meter will not detect.

Example: An adult client of mine, who is using ketogenic diet therapy as a complimentary treatment for her brain cancer, uses a meter to check ketones and glucose. Tracking both metrics over time has helped us to modify her diet to achieve consistency in lower glucose and stronger ketones.

Products: there are only a few companies that make a meter that can check both glucose and ketones. Meters are generally inexpensive but the disposable strips can be cost prohibitive. Many of my clients have chosen KetoMojo because the strips are less costly. 

Breath ketone (acetone) also called “exhaled ketones” is the third method that is available for checking ketones. This method evaluates ketones released from the lungs when you exhale and is easily analyzed by breathing into a tube.

Example: A client with diabetes who exercises regularly prefers this method of monitoring ketosis in addition to checking his glucose. He found that breath acetone was more consistent during exercise than when he checked his betahydroxybutrate which decreased during his exercise but increased later.

There are companies that make portable ketone breath analyzers. KEYTO is a brand that my patients have found helpful. It comes with an App that you sync the device to. KEYTO will give the Charlie Foundation $20 for each purchase of their device when you use the code CHARLIE on their site:


Beth Zupec-Kania

A Registered Dietitian Nutritionist who has managed ketogenic diet therapies since 1991. Designer of KetoDietCalculator, online program for creating ketogenic diets, and prolific author. Beth has trained over 300 medical centers globally on implementing keto diets and has recently published a keto pocket guide for professionals.

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Good Morning,
Thank you for the good work that you do, and for making your keto information available to the public. With the rising popularity, it is requiring greater focus to separate fact from opinion.
I have been in nutritional ketosis for about four years now, as measured by blood ketone levels. I’ve lost about 50 pounds and have had type 2 diabetes go into remission. Hypertension has all but resolved as well and I have reduced or eliminated all prescription drugs.

I have recently noticed that the level of blood ketones is optimum for athletic performance at about 2.5 mml/litre and wondered if there is a ketone level that is best for health reasons. I have had a few serious concussions and still results of them that I’m trying to remediate. Currently I vary from 0.5 to about 1.4 mml/l, and have been as high as 4.2 after 2 days of intermittent fasting.

I wondered if anyone on this blog has an observation to share.


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