Disclosed is a compound which has a low molecular weight and has an activity of enhancing the production of EPO and/or an activity of enhancing the production of hemoglobin. Specifically disclosed is and EPO production enhancer and/or a hemoglobin production enhancer comprising a 1-acyl-4-(substituted oxy, substituted amino, or substituted thio)-1,2,3,4-tetrahydroquinoline derivative, more specifically a tetrahydroquinoline compound represented by general formula (1) [wherein R1, R2, R2′, R3 and R3′ independently represent a hydrogen atom, a C1-6 alkyl group, or the like; R4, R5, R6, R7, R8, R9 and R10 independently represent a hydrogen atom, a halogen atom, a C1-6 alkyl group, or the like; A represents N—R11, a sulfur atom, or an oxygen atom; R11 represents a hydrogen atom, a C1-6 alkyl group, or the like; B represents a C6-14 aryl group, or a 5- to 10-membered heterocyclic group; and n represents an integer of 0 or 1], a salt of the tetrahydroquinoline compound, or a solvate of the tetrahydroquinoline compound or the salt.