Manager Diego Simeone confirmed that no medical clearance has yet been granted.
The Nigerian forward, who joined from Atalanta during the winter transfer window, has quickly established himself as a key figure in Simeone's side.
His impact has been particularly evident in Europe, where he has registered two goals and two assists in six appearances.
One of those goals proved decisive in the quarter-final tie against Barcelona, as Atletico held firm to secure progression despite a fierce comeback attempt at Camp Nou after initially taking a 2-0 lead.
Lookman's contribution in the second leg ultimately helped seal their place in the last four.
However, his involvement against Arsenal now hangs in the balance. Lookman sustained an injury during Atletico's Copa del Rey final defeat to Real Sociedad, where he was forced off in the second half. Since then, he has missed La Liga fixtures against Elche and Athletic Bilbao.
Simeone indicated that a final call on the forward's availability will be made late.
"Well, the truth is that his arrival has had a very positive impact on the team," Simeone said.
"He really does have some differentiating factors offensively.
"He's working much better on his defence. We'll see if he recovers well tomorrow, because he was still feeling some discomfort today. So we'll see if he can help us tomorrow or not."
Arsenal's search for attacking reinforcement has taken a fresh twist ahead of their Champions League semi-final, with Atletico Madrid boss Diego Simeone claiming the Premier League side are interested in Julian Alvarez.
Philipp Lahm believes Paris Saint-Germain will pose a major test for Bayern Munich, whose defensive performance will likely decide the Champions League semi-final.
Diego Simeone has called on Atletico Madrid to show courage and character when they face Arsenal in the first leg of their Champions League semi-final on Wednesday, as the Spanish side looked to recover from their painful Copa del Rey final defeat.
Paris Saint-Germain manager Luis Enrique has insisted no side in Europe is better than his team as the Champions League holders prepare for a huge semi-final first leg against FC Bayern Munich in Paris on Tuesday night.
