This review outlines a number of key issues when performing laboratory testing of homeostasis. The effect pre-analytical variables have on the reliability and consistency of screening tests is often forgotten due to a lack of understanding and awareness. This can be improved through educating healthcare professionals who are involved in taking blood for assessment. Recent advances in coagulation testing have not enabled laboratories to replace the Prothrombin Time (PT) and Activated Partial Thromboplastin Time (APTT) screening tests with more advanced assays and they continue to play an important role with the advantage of being easily automated. However, there are many analysers on the market, each with varying sensitivity to coagulation defects and it is important to keep this in mind when interpreting results.