The 18-year-old has settled quickly since moving to Dortmund, but the club became concerned during the Champions League meeting with Villarreal.
Karetsas was forced off before the half-hour mark in the 3-2 victory after experiencing circulation problems, prompting Dortmund to take a more cautious approach with the attacking midfielder.
According to Sky, Dortmund have now contacted the Greek federation to request that Karetsas is protected during the international period.
The German club have reportedly asked Greece to limit his workload and use him carefully when he is involved against Germany.
Karetsas has started all three of Greece’s Nations League matches so far, including the full 1-0 victory over Germany.
His importance to Ivan Jovanovic’s side means Dortmund’s request could prove difficult to accommodate fully, with the Greece head coach viewing the teenager as an important part of his team.
The timing is particularly significant for Dortmund, who need Karetsas back at full fitness ahead of the return to domestic action.
Werder Bremen are due to visit Dortmund next Friday, giving the club a relatively short window in which to ensure the youngster has recovered properly from the demands of international football.
Karetsas has made a strong impression since arriving in Germany and Dortmund are keen to avoid overloading a player who is still only 18.
The midfielder’s early adaptation has made him an important option for the club, but his international responsibilities now create a balancing act between Dortmund and Greece.
The Greek federation must decide how much involvement Karetsas should have during the international fixtures, while Dortmund will hope their request for a controlled workload is taken into consideration.
Jovanovic is unlikely to want to leave one of his key young players out completely, particularly given Karetsas’ role in the team's recent matches.
For Borussia Dortmund, however, the priority is ensuring the teenager returns from international duty ready for the next Bundesliga challenge.
The club’s approach reflects the need to manage Karetsas carefully as he adjusts to the demands of regular senior football at both club and international level.