Navalny, 44, went on a hunger strike last week to protest what he called poor medical care in a Russian prison.
Navalny, who returned to Moscow in January after suffering a near fatal nerve agent poisoning, is serving two-and-a-half years at the IK-2 penal colony prison.
The avid campaigner was arrested on parole violation charges immediately after returning from Berlin, where had spent months recovering.
But Navalny believes the charges were made to silence his opposition.
Russian authorities have rejected the accusation. Still, labs in Germany and elsewhere in Europe confirmed that Navalny was poisoned with the Soviet-era Novichok nerve agent.
Navalny said in an Instagram post Wednesday that prison authorities have tried to undermine his hunger strike by allowing aromatic chicken to be cooked in his unit’s kitchen, a departure from regulations, and by placing sweets in his clothes pockets.
“Do you know what turned out to be most important in the first stage of the prison hunger strike? Check your pockets,” he wrote..
Navalny’s imprisonment has brought wide criticism from the West.
White House spokeswoman Jen Psaki said Wednesday: “We urge Russian authorities to take all necessary actions to ensure his safety and health,” adding that “we consider Mr. Navalny’s imprisonment on trumped-up charges to be politically motivated and a gross injustice, and we stand with like-minded allies and partners in calling for his immediate release.”
Within weeks of being imprisoned, Navalny said he developed severe back and leg pains and was effectively deprived of sleep because a guard checks on him hourly at night. He went on a hunger strike on March 31, demanding access to proper medication and a visit from his doctor.
Russia’s state penitentiary service has said that Navalny is receiving all the medical help he needs.