Measuring Ketones

An important aspect of the Ketogenic Diet is knowing how high your ketone levels are. There are three types of Ketones; beta-hydroxybutyrate (BOHB) which is measured in the blood, acetoacetate (AcAc) which is typically measured in the urine, and acetone which is typically measured in the breath.

• Measuring Acetone in the breath is becoming a good option, and I believe that this is probably the future of ketone measurement. It's an area of rapid development, and it was not available when I performed my Ketogenic Experiment, so I'm still gathering data.
• Measuring BOHB is the most accurate, and it's now practical at home using a similar technique to measuring blood glucose, but it's really expensive at several dollars per test.
• The easiest and cheapest technique is to measure AcAc in the urine using a test strip. However, this approach is too inaccurate to be useful.

1 Measuring Acetone

Main article: Breath Acetone Meters

Acetone can be measured in the breath, and there is good evidence that there is a strong correlation between breath acetone and blood BOHB ketone levels. In fact, the evidence indicates that breath acetone is a well correlated with even non-ketogenic fat burning, and that it's good evidence of effective weight loss.

The relationship between breath acetone and blood BOHB from multiple studies.

2 Measuring beta-hydroxybutyrate (BOHB)

BOHB is measured in the blood using a small meter similar to a Blood Glucose Meter. A test strip is placed in the meter and a drop of blood is added. After a few seconds, the meter will indicate the level of Ketones. There are two meters on the market in the US, the Nova Max and the Precision Xtra.

• The ketone test strips for Nova Max are cheaper (around $27 for 10 strips), but less accurate and there tend to be a high number of 'bad' test strips. .
• The ketone test strips for the Precision Xtra are far more expensive (around $58 for 10 strips), but better quality. .
• The best option I've found is to order the Precision Xtra strips from Canada for $23 for 10 strips. I've ordered from the Ketone Strips from Universal Drugstore many times and I've been pleased with their service. It takes a couple of weeks for delivery, and shipping is $7.
• You have to draw a drop of blood for this testing, and I'd recommend the Owen Mumford Advanced Lancing Device . It's not much less painful than other lancing devices, but every bit helps. I also use the narrow (33) gauge BD Ultra-Fine Lancets .

3 Measuring Acetoacetate (AcAc)

AcAc is typically measured in the urine using a test strip, which check for 10 different things in addition to AcAc, including trace blood, hydration status and urine acidity. (It's important to test for trace blood in your urine if you're on the ketogenic diet to detect Kidney Stones early.) The test strips are cheap, costing around $0.20 each. . However, AcAc levels tend to correspond poorly to blood ketone levels. During Ketoadaptation, I've found urine levels can be 4x higher than blood ketone levels, but after adaptation the urine levels tend to drop much lower. Hydration status also greatly affects urine ketone levels, and of the levels you're detecting are based on the urine produced since you last emptied your bladder, so they can be quite delayed. See below for a more detailed look at the problems with measuring urine ketones.

4 My Results

I measured my blood BOHB, urine AcAc (using (KetoAnalysis), and my blood glucose. The charts below show the relationship between the values, with the regression line in blue and the 95% confidence intervals shaded. As you can see, for my readings there is better correlation between blood glucose and blood BOHB than there is to urine AcAc. I tried adjusting for hydration using the Urine Specific Gravity values from the test strips, but this made little difference to the correlation. Multiple regression of blood glucose and urine AcAc to blood BOHB did improve the model to r²=0.73.

My blood BOHB against my urine AcAc levels. r2 is 0.43, p < 0.001.

My blood BOHB against my blood glucose levels. r2 is 0.68, p < 0.001

5 Problems with Measuring Urine Ketones

In the past the only viable method of measuring Ketones was to use a Urine dipstick, but this is too inaccurate to be useful.

• Urine dipsticks require you to match the color of the test strip against reference patches, so it is not particularly precise. Using image analysis (KetoAnalysis) can help somewhat. (The test strips use a nitroprusside reagent which changes color from pink to maroon. The addition of hydrogen peroxide does not improve the ability of the urine tests to detect BOHB.)
• Worse, there is evidence that the values read from urine dipsticks overestimate the level of ketones in the urine. A study that compared the values from Ketostix with an enzymatic test found the formula "urinary acetoacetate = 0.40(dipstick value) + 0.15" would help correct the overestimation.
  

  The level of AcAc in the urine is not accurately measured using dipsticks.
• To compound matters further, urine levels do not reflect blood levels of AcAc very well.
  • High level of hydration will dilute urine ketone levels.
  • Kidney function can change the urine levels as the kidney will reabsorb AcAc. With starvation ketosis, the kidneys increase the reabsorption over time, with one study showing a progression of AcAc reabsorption from 47 (+/-10) mumoles/min on day 3 to 106 (+/-15) on day 10, 89 (+/-10) on day 17 and 96 (+/-10) on day 24. Most studies demonstrate no maximum reabsorption rate.
  • There is also a time delay if the blood levels are changing, this will not be reflected in the urine levels immediately.
  • A study indicated that the level of urine AcAc and blood AcAc vary in a non-linear manner, following the equation "y = 0.3x^0.6 + 0.07" (after correction), but r² was only 0.59 .
    

    The levels of AcAc in the blood and urine follow a non-linear relationship.
• Further problems arise because the levels of AcAc can be quite different to BOHB levels, as shown below. A study of children using the Ketogenic Diet for epilepsy showed that when blood BOHB levels are over 2 mmol/l, urine AcAc dipsticks indicate levels of 80-160 mmol/l.

Changes in blood ketone levels during progressive starvation.

• Finally, false positives can occur for a number of reasons.
  • Pigmented urine (trace level only).
  • Vitamin C.
  • Low urine pH (acidic).
  • Increased urine specific gravity.
  • Phenolphthalein (a laxative used in many preparations under various trade names).
  • The amino acid L-dopa.
  • Drugs, including
    • Drugs Levodopa, Bendopa, Brocadopa, Larodopa (all used to treat Parkinson's disease).
    • Glucocorticoids.
  • Fever or burns.

6 See Also

• The classifications and types of Low Carbohydrate Diet.
• An introduction to the Ketogenic Diet.
• My experiences with ultrarunning on the Ketogenic Diet
  • How the Ketogenic Diet can be used for the treatment and management of disease.
    • Using the Ketogenic Diets to mitigate and treat Epilepsy
    • How Ketogenic Diets might help with Cancer
    • A look at the possible mechanisms of action of the Ketogenic Diet
  • Health Risks of the Ketogenic Diet
    • Health Checks for the Ketogenic Diet
    • Supplements for the Ketogenic Diet
  • The time frame and changes that occur with Ketoadaptation
  • What are Ketones
    • How to measure Ketones
    • What ketone levels to aim for
  • The pros and cons of the Ketogenic Diet for athletes
    • The Science of Ketogenic Exercise
  • The Types of Ketogenic Diet
    • The "traditional" Ketogenic Diet based on the Ketogenic Ratio
      • The ways the Ketogenic Ratio can be calculated
        • The different definitions of Net Carbohydrates
    • Low Glycemic Index Treatment
    • MCT Diet
      • MCT
    • Modified Atkins Diet (M.A.D.)
• My Ketogenic Recipes
• Non-Ketogenic Low Carbohydrate Diets