The length of time that blood samples can be kept refrigerated varies depending on the type of blood sample and the tests that are run on it. Blood can be stored as whole blood or as blood fractions and with or without preservatives. Different types of analyses require different storage conditions. Also, since all laboratories do not have the same protocols, getting a conclusive answer is difficult.
According to the National Institute for Health and Welfare in Finland, whole blood samples drawn for clinical exams should be refrigerated to 4 degrees Celsius and can be stored at that temperature for up to seven days. However, serum and plasma samples should be analyzed as soon as possible and can only be stored at 4 degrees Celsius for three days. Any plasma or serum samples that cannot be analyzed within three days should be frozen at minus 20 or minus 70 degrees Celsius.
In contrast, the Dartmouth Medical Center recommends refrigerating serum samples if they cannot be tested within four hours but does not give a time limit for refrigerated storage of these samples. Specimencare.com cautions against assuming that refrigeration or freezing of samples is the correct method. To make sure samples are stored correctly, it is important to check the protocols in use by the laboratory taking the samples.