Scottish Trace Element & Micronutrient Reference Laboratory

Scotland's specialised laboratory for trace elements and vitamins in health and disease

New reference intervals 2023

STEMDRL reference intervals for some trace element assays where updated on 1/3/23. This followed a review of the latest available literature and will ensure that, where possible, STEMDRL is harmonised with other UK Trace Elements Supra-Regional Assay Service (SAS) laboratories. Sources for these new reference intervals can be found via individual trace element pages (click on assay name below and then scroll down to reference range section).

                               Units                  Previous reference interval       Reference interval from 1/3/23

Plasma Aluminium       µmol/L                          <0.2                                     <0.4

Urine Arsenic              nmol/mmol creat            <30                                      <17

Blood Cadmium           nmol/L                          <37                                       <17

Urine Cadmium           nmol/mmol creat            <1.0                                      <0.9

Blood Chromium          nmol/L                          <40                                       <15

Urine Chromium          nmol/mmol creat            <6.1                                      <2.9

Blood Cobalt               nmol/L                           <50                                       <10

Urine Cobalt               nmol/mmol creat             <1.6                                      <2.5

Blood Lead                 µmol/L                           <0.50                                     <0.10

Blood Mercury            nmol/L                            <30                                       <25

Urine Mercury            nmol/mmol creat              <5                                         <1.4


We recommend following guidance developed with input from the SAS Trace Element group and the National Poisons Information Service (NPIS) when considering what action to take in response to a raised lead, mercury or arsenic result. The guidance can be found here. The following links from the guidance contain suggested action when a raised blood or urine result is found in a non-occupationally exposed individual: 

Urine arsenic

Blood lead

Blood mercury

Urine mercury


Please also note blood lead will now be reported in µmol/L only and not in both µmol/L and µg/dL. If conversion to µg/dL is needed (e.g. when referring to the Health and Safety Executive Control of Lead at Work Regulations, 2002) please see use this conversion tool.

If there are any questions about these changes please contact STEMDRL.


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