Sally Pearson's rival Dawn Harper-Nelson posted an emotional video after she was banned from taking her blood pressure medication.

Olympic hurdles champion Dawn Harper-Nelson has released an extraordinary, emotional video message tearfully saying she feared for her life because sports drug authorities had banned her from taking important blood pressure medication.

Harper-Nelson sobbed as she said she feared for her life because her blood pressure had jumped causing her head aches and blurred vision yet she was prohibited by the US Anti-Doping Authority from taking the medicine doctors had told her she needed.

She is currently serving a three-month ban for taking a prohibited substance which is understood to have been an ingredient in her blood pressure medication. Now she has suffered another spike in blood pressure.

LUCY NICHOLSON Olympic hurdles champion Dawn Harper-Nelson fears for her life because sports drug authorities have banned her from taking important blood pressure medication.

Harper-Nelson recorded a video message seemingly on her phone outside a medical centre. She grabbed at the peak of her cap panicking and in obvious distress at her situation.

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"I just want to say this is not fair, I'm afraid for my life. I'm about to go into urgent care because my blood pressure is really high again and USADA said I can't take the medicine the doctor's giving me and they are giving me a new medicine. This is just not ok.

"My head is bothering me. My vision is kinda blurry and they say my blood pressure is high," she said breaking down in tears.

"I'm scared," she sobbed, squeezing the peak of her baseball cap tight down across her eyes. "People need to be aware this is not cool."

Lost for words right now... pic.twitter.com/hsKPYIANsq — Dawn Harper-Nelson (@DHarp100mH) February 24, 2017

An official from USADA quickly reached out to her on Twitter asking her to contact them so they could help her.

Harper-Nelson had been due to fly to Australia only weeks ago to compete in the recent Nitro series but withdrew suddenly and without explanation. Days later it emerged she had been banned for three months for recording a positive drug test.

Harper-Nelson won gold in Beijing ahead of Sally Pearson, who won silver. The medals were then reversed in London when Pearson won gold ahead of Harper-Nelson.