excess
amniotic, bodily, body, intravenous
brake, cleaning, correction, lighter
windshield, wiper (both AmE)

drain
They drained a lot of fluid from his lungs.

drink
Change your diet and drink plenty of fluids.

lose
replace
It's important to replace fluids and salts that are lost during exercise.

retain
Retaining excess fluid could be a problem.

be
become
remain
keep sth
I think we should try and keep our arrangements fluid at this stage.

extremely, fairly, very, etc.
highly
It's a highly fluid situation.

Fluid is used with these nouns:
grace, milk, movement, situation