Auntie Em has already made a few good points in her answer, so check it out. To add to this, I would also like to mention that certain tests have different reference values according to the lab where it is performed. So, a blood sodium level of 127 may be classed as abnormal in some hospital labs, and not in others. Another thing to mention is that refernce ranges are produced according to the values that 95% of the population will fall into assuming everything is normal. So, even if you have a value classed as outside the normal range, 1 in 20 people also have values like this normally. Human error is responsible for a large proportion of erroneous readings - samples mixed, poorly labelled, wrong tests carried out, improper storage of specimens, etc etc. As such, these may all mean you might have to resubmit samples. As Auntie Em pointed out, your body is dynamic - it is changing constantly. Your blood potassium levels after a gym workout will be markedly higher than before a workout, for example. Even if you laid perfectly still on a bed, your heart rate would fluctuate slightly. So, two readings will almost never be exactly the same. Finally, some diagnoses can only be made following two definitive readings. One abnormal reading is not enough, as all the above mentioned differences may occur. And so a repeat barage of tests are often ordered in order to confrim or definitvely exclude a diagnosis. Yes, it is possible that two different tests were carried out on improperly calibrated machines, as you suggest. But I would state that the cahnces are one of the above mentioned reasons are why your tests were re-ordered.

Yes, I'm sure they do. It could also be poorly trained lab techs. I'm glad you are okay at any rate.

Your doctor probably has a financial interest in the lab. BTW, that's always a good thing to ask about before you agree to tests or treatments...

I worked in a lab. I'm going to have to say that it was probably poorly trained lab techs. State law insists that all lab equipment be properly calibrated and tested.