The Normandy's doctor has noted a group in the refugee camp that has military medical supplies but needs simple civilian necessities. Meet Tactus in the refugee camp to broker a trade.
Walkthrough EditDocks: Holding Area in the Citadel and head to the refugee medical center in Cargo Hold B. There you will find a turian named Tactus on the right hand side. Talk to him.
If you have enough reputation, you'll be able to swap supplies as Chakwas/Michel had suggested. If those speech options aren't available, you can give them away with Paragon bonus. (Asking Tactus to reconsider will result in the same conversation again.) Whichever you decide, speak with the medical officer to finish this mission.
You will gain 5 Reputation, 375 experience, and the Med Bay Surgery intel. If the mission was completed through Charm or Intimidation, you will also receive the Efficiency Increase Medi-Gel Upgrade if the medical officer is Chakwas or an increase to Medi-gel capacity if it is Michel.
Note: For subsequent playthoughs, the Medi-gel increase will carry over. As such, it may be prudent to recruit Dr. Michel on your first playthrough, then Dr. Chakwas on the second.