Christina Applegate's daughter reveals own health condition

Christina Applegate's daughter Sadie has revealed her own health condition.

The actress is living with multiple sclerosis - now her daughter has been diagnosed with postural orthostatic tachycardia syndrome, or POTS.

Sadie, 13, revealed her diagnosis on Christina's podcast, MeSsy, this week.

"I have something called POTS," Sadie shared. "I have no clue what it actually is, but it's something to do with the autonomic nervous system and it affects my heart. When I stand up, I get really, really dizzy and my legs get really weak and I feel like I'm going to pass out."

Sadie went on to explain she had been experiencing symptoms of the syndrome for some time but her complaints had been dismissed.

"I hate it for you my darling. I really hate it for you," Christina, 52, told her daughter. "I'm sad. But I love you and I know you're going to be OK. And I'm here for you and I believe you. And thank you for bringing this to light and awareness."

Sadie, whom Christina shares with her husband, Martyn LeNoble, described visiting the school nurse "multiple times a day" when she was in sixth grade, because she "always felt like (she) was going to pass out".

She said she was often told she was making it up, or that her symptoms were merely anxiety.

"They were like, 'You're doing this to get out of class. It's probably just anxiety. Go back to class,'" she said. "They wouldn't do anything for it."