suggested protocol for investigation of a slightly raised isolated bilirubin in an asymptomatic adult patient in primary care

Last edited 09/2019 and last reviewed 04/2022

Recommended investigation for isolated raised bilirubin in primary care (1):

  • values <1.5 times upper limit of normal (ULN)
    • suggested that should retest LFTs in 1-3 months unless clinical suspicion of disease
      • if clinical suspicion of disease then check the proportion of unconjugated and conjugated bilirubin; if concern about possible haemolysis then test haptoglobin, LDH and blood count with reticulocyte count

  • values >1.5 ULN:
    • it is suggested that confirm proportion of indirect (unconjugated) bilirubin versus conjugated bilirubin; test haptoglobin, LDH and blood count with reticulocyte count
      • Gilbert's syndrome is probable if >70%, unconjugated (and no evidnce of haemolysis): no further testing needed if non-progessive on interval retesting (1)
      • if haemolysis (unconjugated bilirubin > 70%) is suspected then haematology referral (2)
      • if conjugated bilirubin > 50% then consider rare causes such as Dubin-Johnson syndrome and drug induced (2)

  • values > 3 x ULN:
    • it is probable that raised bilirubin is a result of disease process
      • referral and further investigation required
        • consider ultrasound (conjugated >50%) or haemolysis (unconjugated >70%)


  • values up to 20% over ULN are likely to be statistical rather than clinical 'abnormals'
  • referral to secondary care is indicated if bilirubin is raised > 2 ULN (unexplained by laboratory tests) (1)


  1. Clinical Knowledge Summaries (accessed 6/4/07). How should I investigate an isolated 'slightly raised' bilirubin in an asymptomatic adult?
  2. City and Hackney CCG. Abnormal Liver Function Tests (LFTs) in Adults (Accessed 1/9/19)