Mr Navalny has been on a hunger strike for 18 days following his incarceration in February over old embezzlement charges. The opposition leader, who demands medical attention for severe back pain and leg numbness, is at risk of kidney failure and cardiac arrest, according to healthcare professionals.
Anastasia Vasilyeva, Mr Navalny’s personal physician, was one of four doctors who pleaded with prison officials to let them treat the opposition activist urgently.
The professionals wrote a letter stating that recent blood test results showed that Mr Navalny’s potassium had hit “critical levels”.
Dr Vasilyeva shared the letter on Twitter, expressing concerns for Mr Navalny’s health.
She wrote: “Having received test results we, the doctors of Alexey Navalny, address the head of Federal Penitentiary Service.
“Due to critical state of health of Alexay Navalny we express our concerns and our readinness to enter into discussion followed by consilium.”
Dr Vasilyeva also pointed out that the doctors’ previous attempts to contact authorities had not been acknowledged.
She added: “We have been waiting for two days with concerns growing. No response thus far.
“Potassium in blood serum 7.1 mmol/L is both — kidney failure and severe heart-rhythm disturbances, ie ventricular fibrillation to the extent of cardiac arrest.