Free T4 (FT4)

Pathology category

Biochemistry

Code

FT4

Referral code

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Test information

Assessment of Thyroid Function

Note NICE guidance recommends TSH alone is requested for diagnosis of primary hypothyroidism or routine monitoring of adult patients. The laboratory will reflex a FT4 if TSH is outside of the reference range, so it does not need to be requested separately if not indicated.

If pituitary disease is suspected an endocrinology referral is indicated

Guidelines

Overview | Thyroid disease: assessment and management | Guidance | NICE

Pre-analytical

Reference range

0 – 20D: 17.4 – 57.7 pmol/L
20D – 3Y: 9.5 – 17.8 pmol/L
3Y – 19Y: 7.9 – 13.6 pmol/L
Adult: 8.0 – 18.0 pmol/L

Pregnancy, by trimester:
1st: 6.67-14.12 pmol/L
2nd: 5.79-12.7 pmol/L
3rd: 6.11-12.2 pmol/L

Source: Beckman Coulter or adult non-pregnant reference range locally derived

Tube type

Tube type info

Adults: 5ml Serum SST (gold top)

Paediatrics: 0.5ml lithium/heparin (orange top)

Special requirements

Minimum volume

Adults: 0.5 ml

Paediatrics: 0.3 ml

Assay frequency

Run daily at local laboratory

TAT Inpatient (urgent)

TAT Inpatient

48 hrs

TAT GP/Outpatient

48 hrs

Referral lab

Local, Clinical Biochemistry