Text size of HUD is too large.
EDIT: I FIXED IT. Go to control panel, appearance and personalisation, display, there should be a slider for item size, set it to the lowest it will go. Restart your computer, everything on your computer will be tiny, but league will be normal sized.
Several patches ago (maybe early this season), the text size was increased for summoner names over champions and combat text. Now every single HUD text is too large. Here is a link to a screenshot from my last game:
I can't read my opponents stats, I can't read what items he has in the top right of the screen, I can barely read my own stats, I have no idea what the timer for my summoner spell on F is, it is hard to read my CS, I can't see the right digit of the game time.
Things that are not shown in this screenshot that are still issues: skill cooldowns are obscured, additional stats (pressing C) is unviewable, TAB is a mess, item cooldowns overlap each other.
For reference, I played this game with in game 1920 x 1080 (I believe, or something close to this) and my computer resolution was 3200 x 1800. These are the settings I have always used and only had issues with player names and combat text being too large, which was not a huge issue (but annoying nonetheless).
I tried changing the resolution of my screen as low as 1280x 720, and also changed the in game resolution to the same levels (and everything in between). No dice.
I also changed the item size in resolution to as small as possible. No luck.
I changed my intel graphics settings, as another user had suggested a few weeks ago. I switched from balanced to quality to performance with no change in text size. Note: I restarted my client between each change, but I did not restart my computer.
I ran custom graphics settings: from 2x to 16x anisotropic filtering. No change. I turned off anti-aliasing. No change.
I have no idea what to do, but the game is unplayable and I have no intention of playing again until a fix is proposed.