How long do bloods have to clot before spinning?

It is generally recommended that blood samples be centrifuged within 2 hours of collection to prevent clotting. If the sample is not spun (or processed, such as through the addition of an anticoagulant) within 2 hours, the blood may clot and the serum or plasma may not be easily separated. This can interfere with downstream analyses, such as serological assays or ELISAs, which require clear and non-clotted samples.

However, it's important to note that the exact time frame for clotting can vary depending on factors such as the type of blood collection tube used (e.g., EDTA vs. heparin vs. plain), the temperature at which the sample is stored, and the individual's coagulation profile. Some individuals may have longer clotting times than others, which could allow for a slightly longer window before centrifugation.

Therefore, it is always advisable to follow the specific guidelines provided by the manufacturer of the blood collection tubes or the instructions specified in the laboratory protocol to ensure accurate and reliable results.