Poorly 1 year old - any advice please?

Hiya, my 14 month old was in hospital Wednesday night due to extreme sickness. She was okay ish Thursday and yesterday but minimal appetite. She only drunk 8oz water Thursday but back up to about 17oz yesterday. I thought she was getting better, as she drunk about 3/4 of her milk this morning, however she keeps falling asleep… She’s been awake since just after 8am and has already fallen asleep and woken up twice. She usually only naps once a day maximum and her wake windows are between five and seven hours long, so this is really out of character for her… Is lethargy normal after sickness? Or do I need to be concerned?