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Vitamin K deficiency

5-minute read

Key facts

  • Vitamin K is important because it helps the liver make proteins that allow blood to clot.
  • Vitamin K deficiency is rare — adults usually have enough vitamin K because normal bacteria in the gut produce it, and it is also in the fat of many commonly available foods.
  • Not having enough vitamin K in the body can make you bruise or bleed more easily than usual.
  • A blood test can confirm vitamin K deficiency.
  • If you are deficient in vitamin K, your doctor will prescribe vitamin K supplements.

Why is vitamin K important?

Vitamin K is important because it helps the liver make proteins that allow your blood to clot normally, to prevent excessive bleeding. It is also important for healthy bones.

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

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

What are the symptoms of vitamin K deficiency?

Not having enough vitamin K in the body makes you more likely to bleed. You may bruise more easily than usual, or it may be more difficult to stop bleeding after an injury or surgery.

It can also make your periods heavier.

What causes vitamin K deficiency?

Vitamin K deficiency in healthy adults is rare. Most adults with vitamin K deficiency have a serious health problem such as:

People taking antibiotics for long periods of time are also more likely to develop vitamin K deficiency.

How is vitamin K deficiency diagnosed?

If your doctor suspects you have vitamin K deficiency, they will refer you for 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. Your clotting can be checked again after an injection of vitamin K. If your clotting improves after the injection, this is evidence that you have vitamin K deficiency.

How is vitamin K deficiency treated?

If you have vitamin K deficiency, your doctor will prescribe vitamin K supplements. They can help your blood clot normally, and they might help increase bone strength. Only take vitamin K supplements after talking to your doctor first, since they can interfere with some other medicines. Only take the amount of vitamin K that your doctor recommends — larger doses might be harmful.

If you do not have enough vitamin K, it can also help to eat more of the foods listed below. It may be useful for you to see a dietitian.

How is vitamin K deficiency prevented?

While bacteria in your gut produce some of the vitamin K your body needs, you also consume vitamin K from commonly available foods. The best dietary sources of vitamin K are dark green leafy vegetables like spinach, parsley, broccoli, kale, cabbage, brussel sprouts and salad greens.

Green beans, avocados, kiwifruit, vegetable oils (especially soybean and canola oils), yoghurt, fermented food and drinks and some cheeses are also good sources. Eating these foods can help you prevent vitamin K deficiency.

When should I see my doctor?

You should see your doctor if you bruise easily or have bleeding sores or scabs that don’t heal. This could be a sign of vitamin K deficiency.

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Last reviewed: October 2022

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