According to Press Secretary Karoline Leavitt, the White House medical unit conducted tests which revealed that Trump suffers from chronic venous insufficiency. This medical condition arises when the valves within the veins responsible for facilitating proper blood flow against gravity gradually deteriorate and fail to function properly.
Source: https://www.euronews.com/2025/07/18/trump-diagnosed-with-chronic-venous-insufficiency-after-checks-for-lower-leg-swelling