In most English-speaking, metric-using countries, hospitals use the metric system for measuring weight and height, but it's common to still hear imperial units used in casual conversation. In Australia I definitely still hear people talking about height in terms of feet and inches. Weight tends to be in kilograms these days though.

This is fairly new in Canada. 10 years ago (long after the conversion to metric), hospitals and doctors used to speak in feet/pounds. As they have switched to metric fairly recently, I expect people to slowly get used to it and soon starting using metric for height and weight as well.

Britain has switched entirely to metric in healthcare, removing the last "friendly" bit of communicating to patients in Imperial.

The risk of confusion was too high, and there was at least one case of a severe overdose when a weight was accidentally given in pounds rather than kilogrammes.

If an American child was hurt outside the USA, and the parent overheard the nurse saying their weight was 55kg, would they know whether that's accurate? That's why it's important that the same units are used at home and in science.

I recently read a blog post where the author described his current weight and his weight as a student in stones.