Poland international Lewandowski, who scored for a 12th consecutive league game in their 2-0 win against Mainz 05 on Saturday, picked up a knock on his thigh but said he hoped to be fit in time for the match in Dortmund.
"I felt some pain in the final minute [after a first-half knock] and hope it does not swell up," he said after Dortmund secured their Champions League spot for next season. "I hope there's enough time until Wednesday."
Lewandowski is Dortmund's most prolific scorer in Europe this season with six goals and two assists in 10 games.
"The game against Mainz was strange because we also kept thinking of the Madrid game. I want to score at least one goal every time I play and if I can achieve that against Madrid then even better."
For coach Jurgen Klopp's young team, which won consecutive Bundesliga titles in 2011 and 2012, it is a career highlight, with the 1997 Champions League winners back in the last four for the first time in 15 years.
"This is the biggest game so far that my boys will have to play," Klopp told reporters.
"We are ready to give it everything we have against the biggest club in the world because if you reach the semi-final then you obviously want to get into that final," Klopp said.
Real's 3-1 La Liga victory at home to Real Betis on Saturday came at a cost, with full-back Marcelo and midfielder Luka Modric picking up muscle injuries.
Still only 19, the pacy and athletic Varane, who was introduced to the club by former France and Real player Zinedine Zidane, has impressed with a series of mature performances this season, particularly against Real's arch-rivals Barcelona.
"This is a key position, and you must bring some security, that's very important," Varane told the club website. "You must also communicate well and have a good sense of positioning. In this position you play a lot with your head, you have to think a lot, these are important skills to possess.
"We have seen that they [Dortmund] are a very good team. They have not reached the semi-finals by chance, we saw in the group phase that they have a quality squad. We will need to be st
