This happened to me before I was diagnosed with POTS, I had blood drawn for a bunch of tests (not my first time getting bloodwork) and went into a syncope episode w/ arrhythmia. The arrhythmia in my case wasn’t POTS related (separate issue), but the fainting could be a sign of POTS for you. It’s likely from your blood pressure dropping especially after having a large blood supply taken from you. After that episode I’ve always laid down for blood draws, that way the blood doesn’t rush from my

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Do you have POTS perhaps? That wouldn’t show up in a blood test. Although turning blue is a sign of reduced oxygenation in the blood, so it might be cardiac in nature generally.

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