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From Fellrnr.com, Running tips
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AcAc is typically measured in the urine using a test strip, such as the [http://www.amazon.com/Multistix-10-100-Test-Strips/dp/B004WNSZGC Multistix] or the cheaper [http://www.amazon.com/Phinex-Parameter-Urinalysis-Reagent-Strips/dp/B0099WTWTA Phinex Multistix equivalent]. These strips 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 [[Health Risks of the Ketogenic Diet| detect Kidney Stones early]].) The test strips are cheap, costing around $0.20 each.
=Measuring Acetone=
Acetone can be measured in the breath, which would overcome many of the problems seen with urine AcAc measurement. However, there would still be some delay between changes in the AcAc level and the levels of Acetone, as well as differing levels of AcAc and BOHB. However, the simplicity of this approach and possibly the lower cost could be a huge advantage. The first device I've come across is the [http://astore.amazon.com/ketonix-20/ Ketonix]] which is reasonably priced at around $110, but only has a simplistic high/medium/low scale and I've read reports of reproducibility errors (repeated tests giving different values.)
=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 r<sup>2</sup>=0.73.
** There is also a time delay if the blood levels are changing, this will not be reflected in the urine levels immediately<ref name="Laffel-1999"/>.
** A study indicated that the level of urine AcAc and blood AcAc vary in a non-linear manner, following the equation "y = 0.3x<sup>0.6</sup> + 0.07" (after correction), but r<sup>2</sup> was only 0.59 <ref name="Musa-Veloso-2002"/>. [[File:KetoneAcAcUrineBlood.jpg|none|thumb|300px|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<ref name="Gilbert-2000"/>.�[[File:KetonesProgressiveStarvation.jpg|none|thumb|300px|Changes in blood ketone levels during progressive starvation<ref name="Cahill2006"/>.]]
* Finally, false positives can occur for a number of reasons.
** Pigmented urine<ref name="patient.co.uk"/> (trace level only).
