Abbreviations should be kept to a minimum. So a formulation such as the following is not to be recommended (quoted from Spiers 1984):

It requires some years in the profession to grasp immediately that this patient with atherosclerotic heart disease and a history of myocardial infarction, status post-coronary-artery-bypass graft, had an episode of bright red blood per rectum prior to admission for endoscopic retrograde choledochopancreatography!

The abbreviations used in this sentence are probably all accepted in the specialty. But just because an abbreviation is permitted does not mean that you are obliged to use it.

So when should you consider using an abbreviation? Let us take an example. The term nonsteroidal anti-inflammatory drug (accepted abbreviation NSAID) may not warrant abbreviation unless it occurs, say, a dozen times in a paper of standard length.

Some abbreviations are more readily understood than the full forms: DNA, AIDS, laser. Often such abbreviations are accepted in the major bibliographic databases. If so, you are free to use them without definition – even in the title and the abstract section.

Refrain as far as possible from inventing your own abbreviations. Try instead to find substitute expressions. Assume that you have made a study of young mature Sprague Dawley rats. You are now writing the paper and need to refer frequently to this group. You therefore consider devising a more convenient construction, such as the YMSD rats.