Vitamin K deficiency is not common in adults, but can be serious because it stops the blood clotting properly. It can also make bones weaker, and increase a person’s chances of breaking them.

Why is vitamin K important?

Vitamin K is important because it helps the liver make proteins that help blood to clot. It is also important for healthy bones.

Adults usually have enough vitamin K because the normal bacteria in the gut produce it. It is also in the fat of much of the food that we eat. Vitamin K is stored in the liver, so you don’t need a lot of it every day.

See this separate article for important information on babies and vitamin K.

Vitamin K deficiency symptoms

Not having enough vitamin K in the body can make someone bruise more easily than usual. It will be more difficult to stop bleeding after an injury or surgery. It can also make periods heavier.

What causes vitamin K deficiency?

Most adults with vitamin K deficiency have a serious health problem such as:

• diabetes
• chronic kidney disease
• cystic fibrosis
• digestive disorders such as coeliac disease
• a blocked bile duct

Anticoagulants such as warfarin might increase the risk of vitamin K deficiency. 

Vitamin K deficiency diagnosis 

If your doctor suspects you have vitamin K deficiency, they may ask you to have a blood test to confirm it.

• Some pathology services and hospitals measure vitamin K levels directly.
• If that is not possible, you can have a blood test to check how well your blood clots. Next, you have an injection of vitamin K and your clotting is checked again. If your clotting improves after the injection, then you have a vitamin K deficiency.

You might also have other tests if there are other issues to investigate.

Preventing vitamin K deficiency

Most people get enough vitamin K in their diet. The best source is dark green leafy vegetables like spinach, parsley, broccoli, kale, cabbage, brussels sprouts and salad greens.

Green beans, avocados, kiwifruit, vegetable oils, yoghurt, fermented food and drinks, and some cheeses are also good sources.

Vitamin K deficiency treatment

If you do not have enough vitamin K, you’ll be asked to eat more of the foods listed above. It may help if you see a dietitian.

Your doctor might also prescribe vitamin K supplements. They can help the blood clot, and they might help increase bone strength. But don’t take them without talking to your doctor first since they can interfere with some other medicines. You should also avoid taking more than your doctor recommends since this might be harmful.

When to seek help

You should see your doctor if:

• bleeding continues for longer than normal
• you bruise easily
• you break a bone after only a very minor fall or injury