The Dutchman is expected to have tests on Tuesday ahead of completing an initial loan move with a view to a permanent transfer.
De Jong is a long-term target for manager Alan Pardew, who tried to sign the 23-year-old last summer before he opted for a £12.6million switch from FC Twente to Gladbach.
However, the frontman has found the going tough in the Bundesliga and is currently on the periphery of the squad.
Pardew has been desperate to strengthen his striking resources during the current window with Loic Remy only on loan, Shola Ameobi out of contract at the end of the season and Papiss Cisse having been repeatedly linked with a move away from the club this month.
Indeed, reports suggested a swap deal involving he and De Jong could be arranged, although that has been dismissed by the Magpies.
Pardew insisted on Monday that he did not expect Cisse to leave the club this week, although, given his well-founded caution over Cabaye, there can be no absolute certainty.
Should the deal go through, De Jong's first involvement could come in Saturday's Tyne-Wear derby clash with Sunderland.
Gladbach confirmed the development on their official Twitter account, saying:
"Luuk de Jong is not training with the Foals today. The striker is currently on his way to Newcastle for medical checks."
The news came as midfielder Yohan Cabaye prepared to undergo his medical in France after the Magpies agreed in principle to sell him to Paris St Germain on Monday evening.