Using abbreviations is convenient, but sometimes people cannot understand its meanings. Some of them, though, have a meaning known to most people. For example, BMI, body mass index, is a common expression. Others, such as AF, atrial fibrillation, which I do not think that everyone can understands are often used in my workplace. Imagine if you read news which say alcohol may raise your risk of AF, can you know its meaning immediately?
I guess English native speakers always use abbreviations in their life. People are used to abbreviation. but do you feel inconvenient in these situations?