Nej, du behöver inte ett transitvisum så länge du bor i det internationella området, enligt Turkiets e-visum portal
Do I have to obtain a visa if I do not leave the international transit area?
No. You do not have to get a visa if you are not going to leave the international transit area.
Mer av samma från det turkiska utrikesministeriet Saker
Question: I will be flying to Europe. I know that our aircraft will land in İstanbul. I am not planning to leave the transit lounge. Do I need to get transit visa?
Answer: If you will not leave the transit lounge at the airport you are not required to have transit visa. Otherwise, you have to make visa application to the nearest Turkish Representation. Contact information of the said missions can be reached through www.mfa.gov.tr (Ministry/Turkish Representations).