Doubts very much that vaping would ruin your fasting.
I've vaped before all my blood tests, I get them done every few months, and am told to fast. My tests I think really only entail a standard panel blood test though, nothing specific. Liver enzymes, blood cell count, etc...
To be safe, don't vape, or if its in regards to insurance, ide abstain, or use 0MG nicotine.
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