Intro: the age of Do-It-Yourself at-home medical technology

The medico-technological age we’re in goes by many names, such as biohacking, self-experimentation or the quantified self. A lot of it is about tracking biochemical markers and performance metrics that can tell you something about your past and present state, usually in an attempt to predict or change it in the future.

Ketones are one such biochemical marker of metabolism that can be measured in blood, breath and urine (see our What’s a ketone? section for more details). Some people use a ketogenic diet to manage cancer, epilepsy, obesity or diabetes and may find it helpful to monitor their ketone levels. Alternatively, they may simply be curious and interested in physiology. Whatever the case may be, since ketones can be measured in blood, breath and urine, which method might you chose for your circumstance and why?

Measuring blood ketones

The ketone bodies measured in blood are acetoacetate and is β-hydroxybutyrate (BhB), the latter being the most commonly measured. A well-known at-home device for doing so is the Precision Xtra.

It can also measure blood glucose using glucose-specific strips. The portable device can measure BhB concentrations ranging from 0.1 mmol/L (1.0 mg/dL) to 8 mmol/L (or 83.3 mg/dL). Measuring blood ketones is the most accurate method compared to breath and urinary ones but the ketone strips are still quite expensive

One case in which blood ketones are measured is when doctors ask their diabetic patients to monitor their blood BhB levels so as to stay below 0.6 or 1.5 mmol/L. These doctors are worried that a rise above these levels may lead to a pathological condition called diabetic ketoacidosis (DKA).

DKA is distinct from the normal physiological state of ketosis, where insulin is doing its job of maintaining stable blood glucose levels and keeping fat from flowing out of fat cells too fast. DKA occurs when insulin can’t keep blood glucose from rising and can’t stop excessive fat from flowing out of fat cells, resulting in uncontrolled increases in blood glucose and blood BhB. One threshold for DKA has been determined at ≥13.9 mmol/L for blood glucose and 3.0 mmol/L for blood BhB (1).

Measuring breath ketones

The ketone body measured in breath is acetone, the same molecule giving some nail polish their characteristic strong smell! People describe its odour in breath as sweet or fruity (that may be a bit generous).

So does measuring breath acetone tell you anything useful about your metabolism? Yes, but it’s inaccurate compared to blood BhB measures (see Accuracy vs Precision below).


The relationship between acetone in breath and BhB in blood is nonlinear, meaning that an 1% increase in one does not result in a 1% (proportional) increase in the other. This is visible in the graph below: as breath acetone increases, blood BhB increases to a lesser extent, which is why the curved line gets less steep with increasing concentrations.


The way the points are distributed around the line, representing measures of both ketones, indicates that less than 0.5 mmol/L of BhB in blood and less than 100 nmol/L of acetone in breath, breath acetone is relatively precise but not accurate. Above those lower values, breath acetone is even less accurate.

Practically speaking, measuring breath acetone can tell you if you are ‘in mild ketosis’ or not, but cannot quantify how deeply ketotic you are (2). You can measure breath acetone with a Ketonix device (disclosure: I own one). Consequently, it’s most useful for people trying to establish a ketotic baseline without needing to know with great accuracy or precision just how deeply ketotic they are.

Although it is often assumed that ketones are higher during a fast than after a ketogenic meal, this isn’t always true. Breath acetone levels can increase after a properly ketogenic meal.

Why measure urinary ketones?

Urinary dipsticks like the Keto-Diastix® detects the ketone body acetoacetate present in urine. One side of the dipstick has a nitroprusside reagent that reacts with acetoacetate, changing the color from pink to gradations of maroon

The more maroon the dipstick, the more ketones are present in the urine. In comparison, when acetoacetate is measured by enzymatic methods in a lab, the at-home urinary dipstick methods tends to significantly overestimate the amount of acetoacetate in urine.

This may be due to hydration levels and fluctuating acid-base balances affecting how kidneys excrete ketone bodies. Nevertheless, this does not mean the dipsticks are useless. In fact, similar to the breath acetone method, it can detect mild to moderate ketosis but cannot accurately quantify it beyond approximately 0.5 mmol/L of urine acetoacetate and 0.5 mmol/L of blood BhB (see graph below).


Especially once urinary acetoacetate has been measured along with blood BhB measures, then dipsticks are a cheap and decent option to see if you’re ‘in or out’ of mild ketosis. According to the particular use a person requires, matching the gradations of maroon with blood BhB levels makes urinary dipsticks even more useful.

For instance, long-term fat loss requires normalization of appetite and hyperinsulinemia, two things which a well-formulated ketogenic diet can do for a growing number of people. But does this mean that the more ketones we have in our urine the more fat we lose? This begs the following question…

What’s the correlation between ketones and fat-loss?

The more ketones you produce does not linearly correlate with how much fat you lose. So no, ketones do not mean ‘fat-loss’. It is important to remember that ketogenic diets can be used to lose, maintain or gain fat, so deep ketosis doesn’t equate to rapid fat-loss.

Ketosis is not a measure of fat-loss, it is more like a measure of fat burning. More specifically, it reflects the ratio of two molecules called oxaloacetate and acetyl-CoA.

However, ketones have interesting effects on feeding behavior since they can normalizing appetite (3), which goes a long way towards normalizing metabolism and hence body composition. A good but imperfect rule of thumb is that, if your urinary dipstick is a color equivalent to approximately 1 mmol/L (10.2 mg/dL), you’re most likely in mild to moderate ketosis (see color gradation example below).


Regarding ketones and weight loss, one important point to drive home is that ketones can be increased by taking over-the-counter stimulants since these tend to increase the release of fat from adipocytes. On the surface, this may seem like a viable solution. Unfortunately, stimulants are not long-term solution to fat-loss.

Our biology will strive to maintain the (excessive) fat mass despite the activity of the stimulants on fat tissue because the fundamental metabolic or endocrinological dysregulation is not addressed. The lesson here is two-fold:

  1. don’t go chasing ketones, but…
  2. get to know your metabolism – if you adopt a ketogenic strategy, what degree of carbohydrate or caloric restriction do you require to enter mild ketosis?


  • Blood BhB measures are the most accurate but also the most expensive and can be substituted for urinary dipsticks to detect mild to moderate ketosis.
  • Short-term fasting produces mild ketosis as measured by the concentration of acetone in the breath, but eating a properly formulated ketogenic meal can moderately boost ketones in the short-term. The Ketonix device is reusable and quite useful for detecting mild to moderate ketosis.
  • Different ketone measuring devices can now be bought online. If you buy them, choose them according to your financial and medical needs.


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