Treatment: clozapine

Psychiatry and addiction medicine · Treatment monitoring · updated 2026-10-30

BioMG follows French guidelines. Adapt it to the guidelines and the tests available where you practise.

Frequency: In France, the clozapine dispensing rate averaged 0.8 per 1 000 people aged 16 and over across areas of residence (0 to 4.9), based on national health insurance reimbursements 2006-2013; old data, dispensing rate and not a national headcount ^[1].

Monitoring on clozapine: first year

Laboratory tests

FBC
First FBC within the 10 days before initiation: neutrophils ≥ 1.5 G/L required (≥ 1.0 G/L in case of confirmed benign ethnic neutropenia).
once a week from week 0 to week 18 (19 times)
then
once a month from week 19 to week 52 (9 times)
Fasting plasma glucoseif neededThe SmPC recommends a lipid profile at initiation then periodically, and fasting plasma glucose at the start of treatment in patients with risk factors for diabetes ^[2]; detailed schedule in the page “Treatment: antipsychotic”.
Lipid profileif neededThe SmPC recommends a lipid profile at initiation then periodically, and fasting plasma glucose at the start of treatment in patients with risk factors for diabetes ^[2]; detailed schedule in the page “Treatment: antipsychotic”.
Troponin, CRP (if initiation: before treatment, then every week for 4 weeks)if needednon-French guidelineThe German S3 guideline (2025) and an international consensus of 93 experts (2025) measure CRP and troponin before treatment then every week for 4 weeks, the period when the risk of myocarditis peaks ^[3,4]. The French SmPC does not provide for this test and relies on clinical signs, with immediate discontinuation and cardiology opinion if myocarditis is suspected ^[2].
Clozapine level (if stopped smoking, severe infection, drug interaction, suspected toxicity or inadequate response)if needednon-French guidelineThe UK MHRA (2020) and the UK package leaflet advise this test when smoking is stopped or switched to e-cigarettes, with an interaction, severe infection, slow metabolism or suspected toxicity ^[5,6]; the German S3 guideline aims for at least 350 ng/mL in treatment resistance ^[3]; the Australian guideline asks for it when smoking changes ^[7]. The French SmPC flags interactions without providing for a level ^[2]. NABM procedure 1662 ^[8].

Detailed explanation and international comparison (in French): read it in English (machine translation)

Monitoring on clozapine: second year (if no neutropenia)

Laboratory tests

FBC
1 time every 12 weeks (4 times)
Clozapine level (if stopped smoking, severe infection, drug interaction, suspected toxicity or inadequate response)if needednon-French guidelineThe UK MHRA (2020) and the UK package leaflet advise this test when smoking is stopped or switched to e-cigarettes, with an interaction, severe infection, slow metabolism or suspected toxicity ^[5,6]; the German S3 guideline aims for at least 350 ng/mL in treatment resistance ^[3]; the Australian guideline asks for it when smoking changes ^[7]. The French SmPC flags interactions without providing for a level ^[2]. NABM procedure 1662 ^[8].

Detailed explanation and international comparison (in French): read it in English (machine translation)

Monitoring on clozapine: third year onwards (if no neutropenia)

Laboratory tests

FBC
once a year
Clozapine level (if stopped smoking, severe infection, drug interaction, suspected toxicity or inadequate response)if needednon-French guidelineThe UK MHRA (2020) and the UK package leaflet advise this test when smoking is stopped or switched to e-cigarettes, with an interaction, severe infection, slow metabolism or suspected toxicity ^[5,6]; the German S3 guideline aims for at least 350 ng/mL in treatment resistance ^[3]; the Australian guideline asks for it when smoking changes ^[7]. The French SmPC flags interactions without providing for a level ^[2]. NABM procedure 1662 ^[8].

Detailed explanation and international comparison (in French): read it in English (machine translation)

Sources (15)