Mr Hipkins left work early on Wednesday to care for his eldest child, who has been taken to hospital.
The Labour leader revealed in a Facebook post that his children have Von Willebrand disease, an often-chronic disorder in which blood does not clot properly.
"I don't normally talk publicly about my kids because I want them to grow up out of the public spotlight but sometimes it's unavoidable," he said.
"Today my four-year-old is in hospital for some needed treatment, so for the rest of the day while that is happening I'll be working from the hospital while I'm focused on her.
"All going well I'll be back at work soon, but thanks to my colleagues for covering a few engagements over the next couple of days that I'm going to have to miss."
Mr Hipkins, who separated from his wife last year, shares and co-parents two children.
His Facebook page is often flooded with toxic and abusive comments but the universal reaction to his post about his daughter has been one of care.
"First and foremost you are 'Daddy'," the top comment on Mr Hipkins' post read.
"Awesome stuff!.... Wishing your girl a speedy recovery."
Mr Hipkins thanked blood donors in his post.
"Lots of New Zealanders rely on the generosity of those who give blood," he said.
"Thank you to all those who help out people like my little girl."
9°C