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Can fasting effect blood test results?

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alex34388
alex34388

Hi all, i read online that a person should not fast for longer then 6 hours when taking a blood test for bilirubin as it would elevate the result. Is this true, if so does it apply to a conjugated test? Please let me know because i had been fasting for 14 hours when undertaking my test and it was high. Thank you.

0 likes, 2 replies

2 Replies

  • EdEire
    EdEire alex34388

    Posted

    Fasting can indeed alter results...but i will not be able to tell you to what extend in your case without seeing it all...
  • sanya11314
    sanya11314 alex34388

    Posted

    Should not apply to conjugated, but unconjugated part of total serum bilirubin.

    The hypothesis is (no one knows actually), that after prolonged fasting (12hours plus) the emergency fat metabolism 'clogs' up the liver's function to conjugate bilirubin (and get rid out of blood stream by doing so).

    If your conjugated portion is way higher (high is not high, depends how high), it should not be a result of fasting.

    Best is to repeat the test and not fasten 12 hours plus. (Worse is even 24h fasting.)

    Be within 2-6h of fasting for bilirubin values.

    (The problem, for blood fat values this is far too little fasting....and values always done in one blood drawl. So when bili comes back too high after too long fasting, you should simply repeat the test with the best fasting timing for that value.)

    Do not think of a hepatobiliary disease yet.

    Also if you had a conjugated high bilirubin concentration, this would show in the urine bilirubin test (only conjugated gets into urine).

    Please talk to your doc about

    value significance

    repeat of test

    and urine bili test (for confirmation of too high conjugated bili in plasma. It get's excreted into urine if it was the case)

    All the best

     

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