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Grossly abnormal results

At SWLP, each discipline handles how grossly abnormal results are communicated to GPs in a different way, depending on the nature of the test.

Below is information about how each discipline makes decisions about when to contact GPs urgently with results.


Results outside the limits in the table below will be telephoned to GP practices during normal working hours.

From 6pm to 10pm weekdays, and 8am to 10pm weekends and bank holidays, results will be reviewed by a clinical scientist/chemical pathologist, and telephoned to the out-of-hours service if required. Values marked in red are a change from the current telephone limits. These limits do not preclude telephoning of any significantly changed results.

AnalyteLower limitUpper limitUnitsNotes
Sodium≤ 120
≤ 130 if age
under 16 y
≥ 160mmol/L
Potassium≤ 2.5≥ 6.5mmol/L
Glucose≥ 25
≥ 15 if age
under 16 y
Creatinine≥ 350
≥ 200 if
under 16 y
mmol/LResults won’t be
telephoned if
patient or
CKD unless
has increased by
≥ 100 umol/L
previous result
CRP≥ 300mg/L
Calcium≤ 1.8≥ 3.5mmol/L
≥ 250umol/L
ALT≥ 750IU/L
Cortisol≤50nmol/LUnless post
CK≥ 5000U/L
Digoxin≥ 2.5umol/LSample should be
6h post dose
Lithium≥ 1.5mmol/L
Magnesium≤ 0.4mmol/L
Phosphate≤ 0.3mmol/L
Phenytoin≥ 25mg/L
Salicylate≥ 300mg/L
Theophylline≥ 25mg/L
Troponin T≥ 50mg/L
≥ 10 if age
under 16 y
mmol/LResults won’t be
telephoned if
dialysis patient
known CKD
urea increases
by ≥ 10 mmol/L

Results outside the critical limits stated below will be telephoned to the GP out-of-hours (111) service during the overnight period (10pm to 8am). As well as reviewing renal function, samples with high potassium levels will be checked for haemolysis, age of sample, and possible contamination prior to telephoning.

AnalyteLower limitUpper limitUnitsNotes
Sodium≤ 115≥ 160mmol/L
Potassium≤ 2.0mmol/L
≥ 6.5
Potassium levels
≥ 6.5 will not be
if the creatinine is
within normal
Glucose≥ 30
≥ 15 if
under 16
years old
Creatinine≥ 350
≥ 200 if
under 16
years old
mmol/LResults won’t be
telephoned if
dialysis patient or
known CKD unless
creatinine has
increased by
≥ 100 umol/L
from previous
CRP≥ 300mg/L
Calcium≤ 1.5≥ 3.5mmol/L
≥ 250umol/L


If an abnormal result which meets the criteria set out below is detected within office hours a biomedical scientist will contact the patient’s clinical team (consultant or GP).

If the result is detected out of hours a biomedical scientist will call the clinical team for an in-patient or 111 if the request came from a GP. In this case, clinical queries should do through the on-call registrar.

HB≤70 g/l if new anaemia or fall of 40 g/l in 24 hours
Neutrophils≤ 0.5 x 10⁹/L unless patient known to be receiving chemotherapy
Lymphocytes≥ 50 x 10⁹/L unless known CLL
Platelets≤ 30 x 10⁹/L


Any clinically significant results warranting urgent action are telephoned to the requestor at the discretion of a consultant clinical scientist


In microbiology, there are no reference ranges per se. Significant urgent results are telephoned or communicated by other means on the judgement of the clinical microbiologists.

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