How Does It Work?

The Science Behind METRON® 

The reactive particles that make up the test form a chemical reaction when exposed to the acetone in your breath.  The results of this reaction can be easily viewed as a color change.  A purple/pink color signals breath ketones at a level indicative of ketosis (> 0.5 mmol/liter).

Instructions for use

PRIOR TO STARTING:  Wait 15 minutes after last food or drink before testing with METRON®.

Read these instructions in their entirety BEFORE starting the test.

Step 1: Set countdown timing device to two minutes, thirty seconds (2:30).  DO NOT initiate timing.

Step 2: Remove both black caps (“caps”) from the METRON® detector. Place the caps to the side as they will be reaffixed in Step 5.

Step 3:  There are two thin-walled glass ampoules within the METRON® tube.  Locate the ampoule containing the reagent crystals; position your thumb and forefinger over the center of that ampoule and squeeze the METRON® tube with moderate pressure until the ampoule inside breaks. SQUEEZE ONLY ONCE.  DO NOT CRACK OR BEND THE METRON® DETECTOR.

Step 4: (Note: A 30-second breath sample is required at this point; have a timing device ready for tracking)

Hold the METRON® Detector vertically, making sure that the end containing the reagent crystals is closest to the floor. Take a deep breath (inhale). Start timer and immediately exhale FORCEFULLY through the Detector for a total of 30 seconds. NOTE: Two or three exhaled breaths may be used to achieve the required 30-second breath sample, but do not inhale through the tube (i.e. exhale forcefully twice, 15 seconds each; exhale forcefully three times, 10 seconds each).  Multiple exhales should be completed in quick succession. Remember: It is important that you EXHALE FORCEFULLY and DO NOT INHALE through the tube.

When the countdown timer reaches two minutes (2:00) remaining, STOP timer and instruct subject to cease exhaling.

Step 5: Securely reaffix both black caps onto the ends of the METRON® detector. The black caps MUST stay affixed to the Detector for the remaining duration of the test procedure.

Step 6: Locate the inner liquid ampoule. Position your thumb and forefinger over the center of it and squeeze the METRON® tube with moderate pressure until the liquid-filled ampoule inside breaks and releases the liquid reagent inside the METRON® detector.


Step 7: Shake the METRON® detector from side-to-side, vigorously, for five (5) seconds to thoroughly combine the liquid and crystal reagents into a mixture.

Step 8: Shake the METRON® detector in a downward arcing motion, like a mercury thermometer (8a). Most of the reagent mixture should collect at one end of the detector.  Then hold the Detector in a vertical position and tap it firmly on a flat, stable surface (8b) with the same end (the end with most of the mixture) pointing down toward the flat surface. These actions encourage the reagent mixture to settle at one end of the Detector. Keep the METRON® detector in a vertical position. Restart timer to initiate two (2) minute incubation period.

When timer sounds, IMMEDIATELY proceed to STEP 9.

Step 9: Identify the color of the reagent mixture within the Detector. Best color results are observed within 10 seconds of the conclusion of the 2-minute incubation period.




 Positive / In Ketosis: The breath ketone level is equal to or greater than 5 ppm, which is correlated with blood ketone level of 0.5 mmol/l and being "in ketosis/reactive".


Light tan or yellow color is visible; NO PINK or PURPLE color. 

⟶ Negative / Not In Ketosis: The breath ketone level is less than 5 ppm (<0.5 mml="" l="" blood="" ketone="" level="" strong="">not in ketosis/nonreactive".  



What do my results mean?

The body is considered to be in a state of ketosis (utilizing fat for energy, e.g. “fat burning”) when blood level ketone concentrations reach 0.5 mmol/L (Mosby, 2009). 

METRON® is calibrated to change color when acetone levels in breath reach 5 ppm, which has been shown to correlate with the blood ketone concentration threshold of 0.5 mmol/L, indicating a ketogenic state. 

When first trying to achieve ketosis, even with close adherence to your dietary and exercise plan, you may go in and out of what is considered a “state of ketosis,” it may take one to two weeks of utilizing your chosen strategy to enter into a regular or stabile state of ketosis.



Mosby's Medical Dictionary, 8th edition. 2009