The attackers ambushed an ambulance belonging to the regional county government of Mandera, north east of the country, as it transported the patient to a hospital in the county.
"The .... ambulance (was) en-route to Elwak hospital for referral with a patient ... and ... in the company of hospital staff," Mandera's Lafey police station said in a report late on Tuesday.
"They were car jacked by suspected AS (al Shabab) militia and driven towards Somalia ... They are not in communication at now due to network issues."
While the frequency and severity of al Shabab attacks in Kenya have reduced in recent years, the group has in the past targeted security personnel, schools, vehicles, towns and telephone infrastructure in north east and eastern Kenya as part of their campaign to pressure Kenya into withdrawing its forces from Somalia.
Al Shabab has been fighting for more than a decade to topple Somalia's central government and establish its own rule based on its strict interpretation of Islamic sharia law.
Kenyan troops are part of the African-Union mandated peace keeping force ATMIS that is helping defend Somalia's central government from al Shabab.