Introduction: Heparin remains the most widely used parenteral anti- thrombotic. It is a high risk medicine that may cause significant harm including death if not used properly. Heparin has low therapeutic index and is ranked among the top 5 “high alert” medications by the Institute of Safe Medication Practices. Heparin related medication errors can occur at any stage from prescribing, dispensing, administration to monitoring of therapy. Its use should therefore be monitored to prevent possible errors and maximize benefits of use. Aim: The main aim of the study was to conduct a clinical audit of the use of Heparin in adult in- patients at the Rift Valley General Hospital, Nakuru. Methodology: An evidence-based, structured clinical audit tool was developed and used to conduct the audit. The clinical audit was done prospectively by observing heparin administration and monitoring among eligible adult in-patients being managed with heparin regardless of diagnosis. Each patient was followed up for at least three days to assess follow-up administration and monitoring of heparin use. Patient files were reviewed to collect relevant data. The patients and/or care givers were also interrogated on how they feel about the quality of care. A cross-sectional study of in-patient reports of patients managed with heparin was also carried out to assess the prevalence and possible determinants of heparin- induced adverse reactions. Results: One of the outputs of this study was to formulate tools for the conduct of regular clinical audits on heparin use. This was formulated and subsequently used to conduct the clinical audit of heparin use. The overall clinical audit of heparin use at Rift Valley General Hospital (RVGH) was 49.79%. For the cross- sectional part of the study, there was no record of any ADR in 99% of 238 files that were used for data extraction. In the other 1%, there was an indication of complaint like pain but there were no other investigations that were carried out to ascertain the cause of said complaint. Conclusion: Some processes were up to standard and need to be maintained, for example the introduction of warfarin at least four days before the cessation of heparin. However, there were several gaps that emerged that may hinder appropriate heparin use. For instance, all the staff in RVGH who handle heparin at any stage of therapy should be trained on appropriate heparin use. This is because the audit established that none of the staff in RVGH has ever been trained on appropriate heparin use. The management should consider availing standard guidelines and protocols for heparin use and also procure the antidote protamine sulphate. This is because there are no standards or protocols of heparin use in the institution. There was also no protamine sulphate in RVGH during the period of audit. All the staff especially the clinicians should be sensitized on how to identify any adverse drug reactions (ADR) following heparin use and how to handle them and how to appropriately report them. This gap was identified in the cross sectional part of the study which was aimed at determining the prevalence of ADRs following heparin use and establishing possible determinants of ADRs following heparin use.