500 g is over a pound, kind of a lot lol. Did you have it with fat? It could have been the size, but also is the source good? When I first started, for over two weeks I was eating almost a pound of liver for dinner, along with another several ounces of fat. The source was good, it was grass-fed and organic. But it was frozen. So eventually I came down with some flu that knocked me out for like a week.