More and more businesses today focus on building long-term customer relationships with the objective to secure recurring revenues in competitive markets. As a result, management philosophies such as Customer Success have emerged, which underlines the importance of knowing your customers in order to make them stay. A common way of tracking the well-being of a firm's customers is the use of customer health scores. Such tools monitor assembled data and indicate whether a customer is doing fine, or is in the risk zone of ending the business relationship. However, there exists little to no consensus on what customer health actually means, or how to distinguish suitable parameters for measuring this concept. Therefore, the purpose of this thesis has been: To extend the existing knowledge of the business concept customer health, and show how to identify relevant parameters for measuring customer health. To reach this purpose, a study has been conducted at a software-as-a-service company operating in the field of digital marketing; where methods such as semi-structured interviews, ethnography, web survey, data mining execution and statistical analysis have been used. The results show that software usage differs between active and former customers, with the general tendency that a high software usage indicates a higher propensity to stay as a customer. The study concludes that customer health is best defined as "the perceived value a customer experiences when using a product". In addition, the parameters that were found to best indicate customer health at the company studied were linked to customers’ software usage as well as their marketing set-up.