Vitamins in Cucumber. Cucumber is rich in a number of essential vitamins, including vitamin K, also known as the clotting vitamin. Vitamin K is essential for helping your blood clot, and the recommended daily amount is 90 micrograms for adults over the age of 19. half-cup serving of sliced cucumber also contains 12 milligrams of phosphorus, 7 milligrams of magnesium, and 8 milligrams of calcium. Cucumbers are also rich in potassium, containing 76 milligrams per half cup serving of sliced cucumbers.