Thanks to the development of drugs known as antiretrovirals, people living with HIV (PLHIV) can live long, healthy lives. Unfortunately, PLHIV need to take antiretrovirals for the rest of their lives. Antiretrovirals are generally safe but can cause serious side effects in some people, particularly with long-term use. Common side effects are discovered in clinical trials. If a drug causes side effects that are too severe or too common it will fail the trial. It isn't possible to test enough people in a clinical trial to discover less common side effects. These are found by monitoring people taking the drug in the real world. It is also essential that the safety of a drug is monitored in people of all ethnicities because some side effects are more common in people belonging to a particular ethnic group. Our work focuses on the 3.5% of the Ugandan population - 1.5 million people - who live with HIV. At the moment we have very little information about how many PLHIV suffer side effects due to antiretrovirals. The importance of encouraging and enabling healthcare professionals to report drug-related side effects is recognised by the Ugandan government. However, systems for monitoring drug-related side effects have only recently been developed in Uganda and the number of reports is very low. Only 400 reports on side effects due to antiretrovirals were made during the 12-months from October 2018 to September 2019. We urgently need to improve reporting of drug-related side effects due to recent changes in the treatment offered to PLHIV in Uganda. In 2018, Uganda began a programme to rapidly roll-out antiretroviral combinations including dolutegravir (DTG), the new drug recommended by the World Health Organisation (WHO), to PLHIV. Uganda is also rolling-out Isoniazid Preventive Therapy (IPT) to prevent active tuberculosis - the main cause of death in PLHIV. Although DTG has some important advantages over other antiretrovirals, we know that in some people it can cause liver damage, high blood sugar, anxiety, insomnia or depression. In addition, the risk of side effects is likely to be higher when DTG and IPT are taken together. We aim to test whether reporting via a mobile application is effective at increasing reporting of antiretroviral-related side effects by healthcare professionals. If successful, our project will also improve our understanding of which side effects are most common in Ugandan PLHIV and how many people they affect. These are essential first steps in our work to make sure that every PLHIV is treated with the right antiretrovirals at the right dose in the future. The mobile application that we will test is called Med Safety(R). Med Safety(R) was developed by a European drug safety project and adapted for Uganda's National Drug Authority (NDA) by the UK's Medicines and Healthcare products Regulatory Agency (MHRA) but isn't yet widely used. We will recruit 3820 healthcare professionals from 382 HIV treatment centres to: 1) investigate factors that affect the success of rolling out Med Safety(R) among healthcare professionals and how healthcare providers feel about using the application; 2) discover whether using Med Safety(R) leads to more reports of drug-related side effects than the traditional web- and paper-based forms; and 3) whether using Med Safety(R) saves money for healthcare providers. We will also train researchers in drug safety. This project will show whether Med Safety is effective at improving the reporting of drug-related side effects by healthcare professionals. Our learning from deploying the Med Safety(R) application across a population that encompasses large, developed cities and isolated rural areas will be invaluable for wider global efforts in drug safety monitoring. Our strong links with National and International agencies including the NDA, MHRA and WHO will help to ensure that our work improves the safety of PLHIV.