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Laboratory Medicine

General Information / Add On Requests

If additional tests are required on a sample already received in the laboratory, we require evidence that a responsible clinician has authorised the additional test(s). This can be via an additional paper request form or the electronic equivalent.

Blood Sciences

The Blood sciences department will add further tests to existing samples in certain circumstances, for information on the tests automatically added: Click here

Biochemistry York & Scarborough Sites

For details of the Clinical Biochemistry Add-on policy: Click here

Routine Biochemistry blood samples are archived and kept for a minimum of three days. Beyond this, add-on test requests cannot be processed. 

Please note that some analytes are labile and deteriorate rapidly and some tests are not suitable for requesting as ‘add-ons’.  In these cases an add-on cannot be processed and a fresh sample will have to be taken.  Most routine Biochemistry tests are stable for 3 days. Exceptions are:

Tests unsuitable for add-ons:

        Ammonia, Bicarbonate, Glucose, sFlt-1/PIGF ratio, Lactate and HCG

Tests with 24 hour stability:

            Troponin T, D-Dimer, B12, Phosphate, Total Bilirubin, PSA

Tests with 48 hour stability:

            Folate, Ferritin, CK, Osmolality, Direct Bilirubin

To request an add-on test:


  • Add-on tests should be requested via CPD
  • For instructions on how to request an add-on via CPD please Click Here
  • For tests that cannot be added on via CPD or if the request is urgent please phone:
    • York: (01904 72) 6802 option 1
    • SGH: (01723 34) 2351

GP and external locations

  • Non-urgent add-on requests can be made via email using the electronic add-on request form: Click Here
  • Add-on requests can be made by phone:
    • York: (01904 72) 6802 option 1
    • SGH: (01723 34) 2351


Haematology York & Scarborough Sites

Additional examinations may be requested up to 24hrs for some Coagulation and Haematology tests . Plasma Viscosity tests are stable for 5 days.  If requesting additional tests please call the laboratory to add on the test. This must be followed up by an additional paper request form or the electronic equivalent, as this is required evidence that a responsible clinician has authorised the additional test(s). 

Microbiology York & Scarborough Sites

Blood samples for serology are kept for 3 weeks, antenatal samples for 1 years. Needlestick samples are kept indefinitely. We also keep a small number of acute serum samples until a convalescent sample is received. If you want to add further tests to a blood sample we will require an additional request. Please phone 01904 726301 to make arrangements.

Most other samples are kept for at least 1 week before they are discarded.  Some samples are kept longer depending on the tests requested. If you want to add further tests to a sample please ring 01904 725721 (York) or 01723 342288 (Scarborough). We will check if we still have the sample and then add the tests. Please note that in some cases the sample may be unsuitable and we will ask you to obtain a fresh sample.

Web Page updated 24: 30/05/23

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