I bought a keto mojo for my bday and used it for the first time yesterday . My reading was 2.3 which according to the site is really good. With this reading would that mean I am in fat burning and how often do most people test.
Also I want to see how certain foods affect me. How would I do this. Would I say for example use some dairy then text blood glucose one hour after or 2 etc .
When I want to see how a food affects me, I do several tests. First, I generally have a baseline of what my glucose and ketones do in a normal day. Then when I am testing the particular new food, I test glucose and ketones before eating. I take the following measurements:
I look to see any spikes or delayed dropping vs. a baseline from a normal day without the new food. If glucose spikes high early, I know there is a problem with that food. If glucose spikes late, I know there is a problem with that food. If glucose doesnāt really spike, but takes a long time to recover, I suspect a problem with the food and take a ketone reading immediately. If that ketone reading indicates a loss of ketosis, I know there is a problem with the food. If the 12-hour ketone level shows or indicates a loss of ketosis, I suspect s problem with the food and either retest or avoid it forever.
Thanks for sharing your ātesting protocolā. I might also watch for a big dip in glucose levels during the early measurements. I believe that can indicate an over reactive insulin response (the body releasing more insulin than you really need to control the increased blood sugar) and indicate the person is insulin resistant or that the person is particularly sensitive to that particular food.
Thanks Diane, I glazed over the use of different strips for @EZB ās testing methods. 
When would you do a baseline test . When I wake up ( dawn effect) after fasting till noon etc . Itās mostly sweeteners and heavy creams I am worried about also sugar free jello
I would imagine (with regard to testing your response to specific foods) right before you eat the food for which you want to test your response.
I know my baseline from so much testing. For example, I know I will wake up with normal boood glucose readings (<100) and losing ketones (0.4-0.7) at 4:30 am. Whether or not I eat, my glucose will rise to anywhere between 110 and 130 by 9:30 am. Then it will slowly drop to 90 by around noon. If I eat, it will rise slightly and go back. By night, it will be 75-85. Ketones go in the opposite direction, rising to above 1 by noon and then often 1-2 by night. That is my baseline pattern.
Before you start donating blood to determine and/or draw conclusions about ketosis, bear in mind that what you are actually measuring is the concentration of Ī²-hydroxybutyrate, the stable storage mode of the much less stable actual energy packet acetoacetate. There is unfortunately no home device to test acetoacetate directly, at least that I am aware of. So basically, youāre measuring only some of the available fuel, not necessarily used fuel.
There are, of course, many valid reasons to measure Ī²-hydroxybutyrate. Comparison with the concurrent concentration of glucose is one of them, since GKI seems to be a relevant biomarker. But determining how efficiently your system is āburning fatā is not one of them. Many people who have very low concentrations of Ī²-hydroxybutyrate are very efficient fat burners and many who have relatively high concentrations are not. Fat adaptation is a sliding scale, the better your metabolism gets doing it the more synthesis and utilization sych with each other. Since youāre wasting less fuel, you need less of it to get the same work done.
There is solid evidence that breath acetone (BrAce) is a better measure of actual āfat burnā than the concentration of Ī²-hydroxybutyrate.
I have a hard time using the equipment to get reliable breath acetone measurements. Iām certain this is user error, but I can test three times in a row and get three very different readings. Iāve found it frustrating.
First, I agree that learning to use the device (I have both a Ketonix and a cheap breathalyzer) is not as simple as it might seem. I have found that to empty my lungs sufficiently requires a LOT of effort engaging both abdominal muscles and diaphragm. This is a very uncomfortable, and I think necessary, procedure. Clinical and lab devices which use spectrometers, etc. donāt have this particular issue. 
Second, if you can master the technique and do it consistently, then you can safely presume that you are emptying your lungs sufficiently to to get an accurate ppm acetone into the device.
Third, why do you presuppose that successive breath samples must be consistent and are not reliable if not? Weāre dealing with a very dynamic system that changes continuously. For example, Ī²-hydroxybutyrate concentration varies minute to minute. Thatās why itās not a very good biomarker of much other than that youāre in ketosis and synthesizing ketones. Most people only sample once or twice a day and mistakenly think what theyāre seeing is a static concentration.
There is no valid reason to think that acetone would not also change minute to minute both from the āspontaneousā breakdown of acetoacetone (which is technically āfat burnā) and utilization within cells and organs (what we would most likely think of as āfat burnā). Additionally, in the case of BrAce if you empty your lungs taking a sample, itās going to take a few minutes for the deep alveoli to build up the acetone concentration again from blood acetone migrating into the lungs. Thus, you could sample too frequently and not get accurate results.
The importance of BrAce as a measure of āfat burnā are the trend and moving average. The Ketonix mobile app tracks both in addition to the sample points.