Living in scandinavia I've taken vitamin D every winter. But lately started taking it all year. I've been sloppy and it seems to coincide with periods of poor

Living in scandinavia I've taken vitamin D every winter. But lately started taking it all year. I've been sloppy and it seems to coincide with periods of poor energy and a bad mood. I'm not sure if the energy and mood precede the drop in vitamin use or vice versa. But either way I think it's good to supplement if you live up north.