Final answer:
Vitamin K is necessary for proper blood clotting, but excess vitamin K is rare and usually not harmful. Deficiency can lead to continuous bleeding, while toxicity is very rare and may cause nausea and headache.
Step-by-step explanation:
Vitamin K is necessary for proper formation of prothrombin, which is involved in blood clotting. Its deficiency can lead to increased clotting time and decreased blood prothrombin levels, resulting in continuous bleeding, especially during childbirth. However, excess vitamin K is rare and usually does not cause harm in healthy individuals. The average diet contains an adequate amount of vitamin K, and the excess is excreted through urine. Hypervitaminosis, or vitamin K toxicity, is very rare and symptoms may include nausea, vomiting, and headache.