Introduction Haematology laboratories are increasingly faced with requests for add‐on coagulation testing. This study explores extending the specimen storage proposals by examining coagulation parameters on refrigerated citrated plasma retained on a cellular fraction over a 24‐hour period. Methods Sodium citrate (Sarstedt® S‐Monovette 3.2%) specimens from 206 patients in University Hospital Limerick, Ireland were refrigerated immediately post‐analysis and re‐analysed in the centrifuged primary container at 4, 8 and 24‐hour intervals using the Diagnostica Stago coagulometer and reagent combination. Coagulation assays examined for statistically and clinically significant differences included PT, APTT, D‐Dimer, fibrinogen and Protein C. Results PT, APTT and Protein C values displayed statistical significance from 4 hours. Fibrinogen differences were statistically significant from 8 hours. D‐Dimer differences were not statistically significant at any interval over the 24‐hour period. The refrigerated storage limit for PT and APTT results was determined to be 4 hours. D‐Dimer was the only test parameter to report a mean percentage variance >10%. However, result changes at the threshold region of 0.5 µg/mL FEU were found to be within assay precision limits and desirable bias up to 8 hours. Maximum mean differences for Protein C (−1.3%) and fibrinogen (2.3%) were within assay precision limits and desirable biases up to 24 hours. Conclusion PT and APTT results are stable in refrigerated citrated plasma maintained on a cellular fraction up to 4 hours post‐phlebotomy. D‐Dimers results are reliable up to 8 hours, while fibrinogen and Protein C results are stable for at least 24 hours.