Tacrolimus

Targets commonly sit between 5 and 15 ug/L depending on the organ and time since transplant; the transplant team's target applies.

Tacrolimus is the main anti-rejection medicine after most transplants. Because the gap between too little and too much is narrow, the blood level is measured regularly, usually just before the morning tablet (a trough).

Transplant clinics measure it at every visit, and target ranges change over the years after transplant and with the type of organ.

• Taking the tablet before the sample rather than after
• Some antibiotics, antifungals and other medicines as a class that slow its breakdown
• Grapefruit
• Diarrhoea
• Liver disease

• Missed tablets
• Some medicines as a class that speed its breakdown, for example some anti-epilepsy medicines and St John's wort
• A change in formulation or brand

• A sample taken after the tablet reads high
• Ranges differ by organ, time since transplant and formulation
• Different assays give slightly different values

Blood taken just before the morning tablet, 12 hours after the previous one (or 24 hours for once-daily forms).

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.