My school recently made new coat orders available to us (to use as back-ups/replacement for the white coats that we received during first year, which already have a lot of mileage and are starting to look pretty dingy.) During orientation, measurements were taken for our coats, and there were 2 separate sizings for women and men. I was in between a women's small and medium, but opted for the medium because I figured it would shrink when I washed it, I'd want to put lots of stuff in my pockets, etc. Big mistake. Now I look like a giant white box. I have to roll the sleeves up so that I don't drag my cuffs in people's wounds and stuff. It doesn't fit right, and it just feels too big. It didn't shrink in the dryer, either.
This year, our school gave us the option to order some new coats. I jumped at the chance. However, these coats were coming from a different distributor than our old coats, had different embroidering, etc. So, I figured that, to be on the safe side, I'd go with a medium, and just get it altered if I had the same problem. When my 2 new white coats were delivered, I went home to try them on. What the school had failed to mention was that the sizes must have been unisex this time. Where my old white coat just made me look like a box, I was positively SWIMMING in these coats. They are probably too big for many of the males in my class. You can't even SEE that I have hands when I have it on - I look like a preschooler playing dress-up in her daddy's lab coat. I brought it to a tailor, but it was a lost cause - they would have had to remove so much fabric that it would have cost me an arm and a leg, and would have looked really strange and "poofy" in sections where they couldn't take it in. So, I'm out the $$ I spent on these coats, and I'm stuck wearing my old white "box" from first year. Ugh.
If you are a woman around 5'5", 130 lbs, get the small. (Unless it's unisex - then get the extra small.) I'm not a particularly tiny or big person, so I figured that medium would be perfect. Totally wrong.