New research shows that it's almost impossible to overdose on vitamin K. Even though it's a fat soluble vitamin, apparently, the body does have a mechanism of getting rid of excess vitamin K. But it's best to remain within regular limits just to be on the safe side. If overdose symptoms like nausea, headache, fatigue, stomach upset or mood change are noticed, one should stop taking the supplements immediately and drink lots of water.
By the way, I want to mention that vitamin K is not potassium. Those are two different compounds. Some people confuse them because potassium is represented as "K" on the elements table.