The order was passed by special judicial magistrate (CBI) Anil Kant Mani Tripathi on a CBI plea, which had asked for seven-day remand of the doctor.
On May 9, Shukla was remanded in two-day CBI custody till May 12.
He was arrested on May 7 by the agency and was remanded in 14-day judicial custody till May 21.
However, CBI filed a plea seeking his custody for interrogation.
The CBI had arrested Shukla in connection with the murder of his predecessor V K Arya in October 2010.
According to the CBI, the alleged motive behind the murder was the fear of being exposed for "misappropriating funds" in the National Rural Health Mission.
There were indications emerging that Shukla could also be allegedly involved in killing of another Chief Medical Officer B P Singh, official sources said.
Arya was murdered while he was taking a morning walk on October 2010 at Vikas Nagar area while Singh was shot dead in April last year at Gomti Nagar.
Shukla was earlier arrested by the CBI last year in connection with the NRHM scam but was granted bail by the Allahabad High Court.
The court had on July 27 directed the CBI to probe the murders of the two CMOs and also irregularities in implementation of the NRHM Lucknow office.
Lucknow: Former Lucknow Chief Medical Officer A K Shukla, arrested in connection with the murder of his predecessor Vinod K Arya, was on Tuesday remanded in four-day CBI custody by a court here.
First Published: Wednesday, May 16, 2012, 00:15