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Took a blood test at around 45hrs fasted just now. How might that affect my results?

I only really wanted an a1c test, which shouldn’t be too affected since it measures 3-4 months, but what about some of my other results?

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Answer

Very hard to say. Some people’s TriG jumps during fasting. Mine is usually lower than normal.

Also if I don’t exercise for the first \~36h I can have a ludicrous FBG, like 120+, but a half-decent workout \~45hr in may be MUCH lower than normal after a couple of hrs. (This weekend 2 hrs after resistance workout, \~64 hrs in: 56!, recovering to low 70’s a few hrs later.) In a 74hr fast my wife’s BG never indicated under 75.

Your HbA1c will be biased downward by a coupe of days fasting, but the amount is trivial.

Answer

A1c will be unaffected, as you knew. Blood glucose is likely to be way down, but the time of day may make quite a difference (“dawn effect” raises my BG by about 30-50 pts for a couple hours in the AM). The rest will vary greatly, because you were right at the point where your body would be switching from glucose/glycogen to ketones.

FWIW, I did a full blood screen when I was 7 days fasted last summer and my BG was around 75 (my normal is \~100), Total Cholesterol was 137 (vs \~220), LDL was 70 (vs \~140), HDL 38 (vs \~40), and TriG was 146 (vs \~240).

Answer

A lot of results, they say you can’t fast any longer than 16 hours to get accurate results… usually somewhere between 10 - 12 hours is the sweet spot. Talk to your doctor and tell them how long you were fasted for, as the results might be wildly inaccurate.

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