Physical Health Monitoring (Clozapine)


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Mandatory Blood Testing

Due to license restrictions, mandatory blood monitoring must be undertaken in all patients prescribed clozapine. These restrictions apply because a small number of clozapine patients may develop neutropenia.

Patients prescribed clozapine will have full blood count (FBC) measurements taken to the following schedule:

Baseline for registration  
Weekly For a minimum of 18 weeks from start
Fortnightly From the end of weekly monitoring to a minimum of 52 weeks
Monthly For as long as treatment continues post 52 weeks
Twice weekly If an amber result is obtained. Continue until green
Daily If a red result is obtained. Continue until two successive green results

Note: Patients may only progress from weekly to fortnightly or fortnightly to 4 weekly FBC if authorised by the clozapine monitoring service.

Clozapine clinics and wards must have reliable processes for ensuring clozapine FBCs are taken as scheduled.

FBCs are normally sent to the clozapine monitoring service’s laboratory for analysis. 

If samples for patients are analysed locally it is the responsibility of the ward multi-disciplinary team and community based clozapine clinics to obtain that result and communicate it to the clozapine monitoring service and pharmacy and to act on the outcome of that result.

Clozapine discontinuation FBC monitoring will be undertaken as required by the clozapine monitoring service.

Once a FBC is entered, the patient is assigned a coloured "status":

Blood counts (x 109/L) Classification Action
WBC ≥ 3.5
neutrophils ≥ 2.0
GREEN Continue clozapine treatment
WBC ≥ 3.0 and < 3.5
neutrophils ≥ 1.5 and < 2.0
AMBER Increase monitoring frequency to TWICE weekly until GREEN
WBC < 3.0
neutrophils < 1.5
RED STOP clozapine treatment immediately. DAILY bloods until TWO consecutive GREEN results


Side-Effect Monitoring

Clozapine clinics and wards should perform additional side-effect monitoring for each patient prescribed clozapine. This will include:

  • Constipation – at every contact*
  • Blood pressure
  • Pulse
  • Hypersalivation
  • Sedation
  • Incontinence
  • Signs of neutropenia (sore throat, temperature & flu like symptoms)
  • Fits, faints & funny turns

Clinical observation and the Glasgow Antipsychotic Side-effect Scale (GASS- clozapine) should be used. GASS should be undertaken every 6 months and one month after any dose changes are made. The outcome of routine side effect monitoring and 6 monthly use of GASS must be reported to the patient’s responsible medical officer (RMO). 

The clozapine side effect care plan should be used to promote a systematic approach to the assessment of side effects.

* Constipation must be assessed systematically at every contact with the patient. Patients will receive education about the likelihood of becoming constipated, things they can do to minimise the risk and the need to report any change in bowel habits. It is recommended that the Clozapine & Constipation fact sheet from the Choice & Medication website be given to all patients.

Ongoing Management

All patients prescribed clozapine treatment, regardless of setting, should be offered routine monitoring for physical health problems which may arise during treatment. The table below describes the monitoring required.

Parameter/test Frequency Actions if outside range
Full blood count Follow manufacturer's mandatory protocol. Contact mental health pharmacy for advice.
Constipation Assess bowel habits at baseline, any point of blood sampling and ideally at every point of contact. Treat symptomatically and seek help from physicians if complete obstruction or a poor response to conservative laxative treatment.
BMI/weight Baseline, weight during initiation, 3 monthly for 1 year and then annually. Offer lifestyle advice.
Plasma glucose (fasting) Baseline, at 1 month, at month 3 than 3 monthly for 1 year then 6 monthly. Offer lifestyle advice, Obtain HbA1c. Consult with GP and/or specialist as appropriate.
Blood lipids Baseline, 3 monthly for 1 year, then 6 monthly. Offer lifestyle advice and consult with GP and/or specialist for consideration of treatment e.g. statin therapy as appropriate.
Blood pressure Baseline, as per initiation protocol, 3 monthly for 1 year, then annually. Also following dose changes.

If hypotensive: Consider slower titration or dose reduction.

If hypertensive: Offer lifestyle advice and consult with GP and/or specialist for consideration of treatment.

Pulse Baseline and as per initiation protocol, at 3 months and then annually.

Consider slower titration or dose reduction.

If tachycardia persistent, observe for other indicators of myocarditis or cardiomyopathy.


Baseline, 3 weeks, at 3 months and then annually.

Additional ECGs should be performed as clinically indicated.

Act on abnormality according to significance and clinical indication. Refer to cardiologist if in doubt.
Troponin 1 and CRP Baseline, day 7, 14, 21 & 28

Continue clozapine with daily CRP and Troponin 1 monitoring and request echocardiography if any of the following criteria are met:

  • Signs or symptoms of unidentified illness.
  • HR>120bpm or increased by >30bpm over 24 hours.
  • CRP 50 - 100mg/L. 
  • Mild elevation of troponin1 < 2 x upper limit of normal.

Stop clozapine, consult cardiologist and request echocardiogram if any of the following occurs:

  • Troponin > 2 x upper limit of normal.
  • CRP>100mg/L.
Urea & electrolytes Baseline then as clinically indicated. Investigate as clinically appropriate.
Liver function tests Baseline then annually or more frequently if clinically indicated. Investigate as clinically appropriate.
Side-effects 'GASS for clozapine' or other recognised side-effect questionnaire for antipsychotic medication during initiation and regularly thereafter, with general side-effect enquiry at least at any point of blood sampling. As clinically appropriate.
Smoking status Initiation and at regular intervals thereafter, at least annually. Warn patient regarding effect of changes of smoking status on clozapine levels and side-effects. Check clozapine level and GASS for clozapine if change of status.
Women of reproductive age. Pregnancy/contraceptive status on initiation and at regular intervals thereafter, at least annually. In all cases: Pre-pregnancy discussion of pregnancy intentions. Offer advice/signposting on contraception. Early discussion of options if unplanned pregnancy.


Last reviewed: 10 May 2022

Next review: 01 October 2023

Author(s): MHS Clozapine review group

Version: 1

Approved By: PMG-MH

Reviewer Name(s): Lead Clinical Pharmacist, Clinical Effectiveness Pharmacist