The former Spice Girl revealed the ordeal while co-hosting her 2DayFM radio show.
Mel and her daughter Angel
She explained on air, "This morning's been a little bit crazy because my six-year-old, Angel, was not feeling very well yesterday, dizzy and had her first ever nose bleed, so I kept her off school.
"And then this morning, (she was) completely disorientated and blood was just funnelling like there was no tomorrow, so I took her to the emergency room.
"I just literally left there like half an hour ago. She had a blood test, a heart murmur thing on… poor little thing."
The former Spice Girl with children Angel, Phoenix and Madison (from left)
Unfortunately, the singer still doesn’t know what is wrong with her little girl. "(The doctors) don’t know, they’ve just done a bunch of blood tests so we're just waiting for that stuff to come back," she said. "But they're thinking it's either some kind of a heart murmur or a vessel infection or sinus infection.
"A lot is going on!" said the star, who said she felt completely "helpless" while waiting at the hospital with Angel.