How are doctors able to determine the levels of say your cholesterol, triglycerides, glucose etc. through a few blood samples from one site? I can’t imagine all of the stuff would be in the one area you’d take a blood sample from, right?
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>I can’t imagine all of the stuff would be in the one area you’d take a blood sample from, right?
But it is.
Things that end up in your blood are never dumped in one go but released over time, and constantly getting mixed on top of that since everything passes through the heart again eventually. And triglycerides/glucose are especially prevalent –> easy to measure.
For perspective: the research lab I work in can do measurements of specific antibodies off of just a few drops of capillary blood from fingersticks. It performs exactly as when you get the sample from a 10 mL venous draw instead — we tested that extensively — and from that whole blood sample, we dilute >1000x further for actual measurement, too. That’s how homogenously distributed things are, and you can really go very far before you run into the sort of sampling error you’re thinking of (for my lab’s assays, the sensitivity of the test becomes a problem before sampling error does).
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