Costa, who has scored nine Premier League goals since joining from Atletico Madrid during the close season, has been dogged by niggly injuries in recent weeks and picked up a groin strain while on international duty with Spain.
However, according to media reports the 26-year-old, who has missed Chelsea's past two games against Crystal Palace and Maribor, spent time in hospital with stomach pains after the international break.
Loic Remy has led the attack for Jose Mourinho's side in the absence of Costa but the French striker picked up a muscular injury after scoring Chelsea's opener in their 6-0 Champions League win over Maribor on Tuesday.
As Chelsea's only fit senior striker, Didier Drogba is likely lead the line for the table-toppers when they travel to sixth-placed Manchester United on Sunday (local time).
