Sergio Aguero was taken to hospital after fainting at half-time of Argentina's friendly defeat to Nigeria on Tuesday.
Argentina coach Jorge Sampaoli said the Manchester City striker "got dizzy" during the break after his tap-in gave doubled La Albiceleste's lead.
The Argentine Football Association wrote on Twitter that Aguero "presented symptoms of fainting and for that reason he was taken to have routine studies done as a precautionary measure."
Dario Benedetto replaced Aguero in the lineup, but Nigeria rallied with three second-half goals to win 4-2, handing Argentina their first friendly defeat since November 2014.