Abstract: The present disclosure relates to a method of increasing fertility of a male subject, wherein the male subject suffers from reduced fertility resulting from a medication, wherein the medication inhibits sperm cell production by inhibiting spermatogenesis in a testis of the male subject, and wherein the method comprises administering to the male subject an effective amount of an extract of Costus speciosus in combination with the medication to prevent, and/or reduce the inhibition of sperm cell production by the medication to increase the fertility of the male subject.