How to arrange therapeutic drug monitoring in England

Katerina Galkina · EN · 07/10/2026

Therapeutic drug monitoring measures a specific medicine's concentration to answer a clinical question. A general blood panel does not replace it, and a laboratory range alone cannot determine treatment. The clinician responsible for prescribing should lead the plan.

Supply the overseas monitoring plan

Show your GP or UK specialist the prescription, active ingredient, formulation, dose, administration times, recent changes and previous results. Establish whether a drug level is needed and what other checks apply.

Not every medicine needs routine concentration testing. NHS SPS, for example, advises against routine serum digoxin levels without particular circumstances. NHS SPS: digoxin monitoring ↗. Decisions depend on the drug, symptoms and situation.

Agree exact sampling time

Medicines differ in the required interval after a dose, stable-dosing requirements and timing after dose changes. A randomly timed sample may be unsuitable.

Obtain written prescriber instructions about preceding and subsequent doses. Do not omit medication yourself. Record actual dose and collection times, illness, dehydration and new medicines. Drug-specific guidance such as lithium monitoring ↗ illustrates why there is no universal instruction.

Find a laboratory for the assay

For NHS requests, follow the specified collection location and timing. Privately, confirm the analyte, sample type, referral, special handling and turnaround. Establish whether clinical review is included and who receives urgent findings.

Ask whether kidney function or other measurements are required simultaneously. The treating team decides this; do not order someone else's protocol. Keep units, methods and dates for overseas results.

Obtain a prescribing decision

Give the result to the responsible clinician and agree continuation, dose adjustment or repeat testing. Do not change doses using an online table: laboratory ranges cannot capture every clinical factor.

Possible toxicity, significant illness or accidental extra doses need urgent advice rather than waiting for routine testing. Give the medicine, dose and timing; call 999 for danger to life. Obtain a continuing UK monitoring and prescription plan so care does not depend on isolated private orders.