Apart from the latency of diffusion from bloodstream to interstitial fluid (and the lower levels in the interstitial fluid) the FDA requires that consumer devices be with 20% of the venipuncture level.
That means a lancet poke can be quite different from a meter like the freestyle, and both can be quite different from the level in your veins that a lab would get. So if your level is 200 one device can read 240 and the other 160 and both can be considered “correct”.
I found that the freestyle libre 2 and libre light are characteristically low while the FS 3 is characteristically high. So I use them for the shape of the curve, and that is useful.
That means a lancet poke can be quite different from a meter like the freestyle, and both can be quite different from the level in your veins that a lab would get. So if your level is 200 one device can read 240 and the other 160 and both can be considered “correct”.
I found that the freestyle libre 2 and libre light are characteristically low while the FS 3 is characteristically high. So I use them for the shape of the curve, and that is useful.