The group said the doctor attending to the Sheikh has passed the warning to the authorities but the federal government has refused to let him have access to proper care, according to naj.com website.
It appealed to Nigerians to join them in mounting pressure on government to release the senior cleric.
"The way and manner in which the federal government has been handling the health of the fatally injured Sheikh Zakzaky for the past 13 months leaves much to be desired,” the IMN said.
The group said the federal government has also refused to let the Sheikh’s personal doctor visit him. "Thus far, the government has decided to play deaf, dumb and blind, as if all is well.”
The group has also called on Acting President, Prof. Yemi Osinbajo to obey a court order and free Sheikh Zakzaky.
A December ruling by an Abuja court called the detention of Sheikh Zakzaky and his followers illegal and unconstitutional.
The Nigerian court imposed a 45-day deadline for the release of Sheikh Zakzaky and hundreds of his supporters. The deadline has expired.
Sheikh Zakzaky was arrested more than a year ago during raids by the Nigerian army on peaceful gatherings of IMN members in the northern city of Zaria. Human rights groups say nearly 350 IMN members were killed in the army raids.