"Divya Putrajeevak Seed", sold in Patanjali Pharmacies, a chain of shops owned by Ramdev, is described in catalogues as a natural herb for treatment of infertility.
It does not promise a male child, but the name is misleading, allege doctors who point out that "Putrajeevak" means "son's life."
Some Ramdev stores claim that the medicine, available for Rs 35 a packet, helps ensure that a boy is born. The claim is not supported by the text on the packs, but even then, many customers allegedly come to buy the drug with the hope for a boy.
"Those who have a boy tell others that they had a boy because they took the medicine from us," says Dr Shyam Sunder, who works at a Ramdev medicine store.
"The message we get from Swamiji (Ramdev) says that if you're not having a son then you can take this Putrajeevak medicine which may help you," he told NDTV.
Ramdev, who supported the BJP's national election campaign last year, was recently named the ambassador of Haryana by the state's BJP government.
"Some people do come saying they want a male child but I tell them you can't ensure a boy but yes, it helps in infertility and like with any disease there is a chance," said Dr Suprita Sharma, an ayurvedic doctor who often prescribes Ramdev medicines.
Amid India's battle to stop the dwindling number of girls, the Supreme Court this week ordered Yahoo!, Google and Microsoft's Bing to stop displaying ads for sex determination tests.
India's child sex ratio dropped from 964 in 1971 to a low of 918 in 2011, according to the UN, which calls it a national emergency. Between 2001 and 2011, the decline was seen in more than two-thirds of the districts in the nation.