Sellassie Blackwell was rushed to the hospital Wednesday afternoon.
Blackwell posted a picture of himself at the hospital. He suffers from a blood disorder.
The five hunger strikers entered their 14th day without eating to protest police shootings.
Blackwell talked about his weakening health Wednesday morning
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"Our health is declining very fast. We are very concerned about that. So, hopefully won't be so stubborn and really wants to meet with us.," Blackwell said.
Mayor Ed Lee tried to meet with the hunger strikers on Monday but his offer was rejected.
The protesters then marched to City Hall Tuesday, but could not meet with Mayor Lee.