The defender started 31 of Sporting's 38 La Liga matches last season, but could not prevent Los Rojiblancos from being relegated to the Segunda Division.
Barcelona have been strongly linked with a move for the 20-year-old ahead of the 2017-18 campaign, but Malaga are said to lead the Spanish interest as the centre-back prepares to leave the club that he joined at the age of 13.
"There are several options, it can be one or another. I'll make a decision today. Malaga are there, as are other clubs," Mere told reporters. "It's clear that Spain is a nice place to play, but so is going abroad and trying out another country. I'm nervous about it, but I have to make a decision.
"I've been thinking for 20 days and I haven't gone a day not thinking about it. My head is all over the place and I don't know what decision to make or what to do. The club received a few offers, but they were rejected and I respect that. That's why I say that I don't know the conditions on which I'll leave.
"I made this decision a few days ago. I'd rather not go through it. Gijon's where I'm comfortable. It's been very hard for me and you never know if you're going to get it right. I killed myself for Sporting's badge. It's my character, my way of working. And I know to whom I must be grateful. Sometimes you have to make these decisions, even if they're difficult. It's what it is."
Mere, who helped Spain Under-21s make the final of the Under-21 European Championships this summer, is understood to have a £13m release clause inserted into his Sporting contract.