T4 (Total Thyroxine)

LABOKLIN Service ID: 137


serum or heparin plasma 0.5 ml resp. 0.4 ml (small mammals)




1 day


  • Dog: For the diagnosis of hypothyroidism. As a single value, it has only limited diagnostic significance. Determination should therefore always be performed in conjunction with fT4 and TSH. Alternatively, a TRH stimulation test can be performed.
  • Cat: For the diagnosis of hyperthyroidism, which is the most common hormonal disease in elder cats and which entails extensive sequelae (tachycardia, chronic diarrhoea, cachexia). Usually sufficient as a single parameter, in questionable cases, TSH can be determined additionally.
  • Therapy control dog/cat: Blood sampling 4 hours after administration of thyroxine (dog) resp. 3 weeks after therapy start (cat)
  • Birds and reptiles: Values are physiologically often very low below the detection limit of the test system used); in this case,determination of fT4 is recommended.
  • Horse: If (very rarely occurring) hypothyroidism is suspected, determination of T4 and T3 with a subsequent TRH stimulation test is recommended.