The bearded fugitive, 63, is said to have made so much money curing a variety of ailments that he was about to start a new life in Russia.
Mina Minic, his tutor in Serbian capital Belgrade, said: "He learned quickly and soon became a name in his own right. He was preparing to move to Russia but decided to stay to learn more from me. It seems he left it too long."
Karadzic also visited Italy and treated a couple in Austria who were having trouble conceiving, The Sun reported.
The wife became pregnant, but the husband said: "I didn't like him, he was arrogant, never looking you in the eye."
He had stolen the identity of retired bricklayer Dragan Dabic, who lives in the northern town of Ruma.
Secret agents revealed the scam to Dabic, 66, who said: "I thought it was a joke, we don't even look alike."
The ex-Bosnian Serb leader, accused of the massacre of 20,000 civilians in the 1992-95 civil war, was arrested in Belgrade on Monday.
Karadzic is accused of planning massive civilian massacres, described by the United Nations war crimes tribunal as "scenes from hell, written on the darkest pages of human history."
Karadzic's 11 charges included one of genocide and one of complicity in relation to the Srebrenica massacre of Bosnian-Muslim men.