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Vitamin K deficiency

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Vitamin K is an essential nutrient that we need in our diet. Not getting enough can lead to a deficiency and cause health complications.

What is vitamin K and what does it do?

Vitamin K is an essential mineral that has several varieties, including K1 and K2.

Type K1 is found in leafy green vegetables, vegetable oils, and cereal grains. This is our main dietary source of vitamin K. Type K2 is found in small amounts in some meats and fermented foods. It’s also made by bacteria in the gut.

We need vitamin K in our diet because it helps with blood clotting and wound healing. It’s also thought to help keep the bones healthy.

The NHS recommends that adults need one microgram (mcg) of vitamin K for every kilogram of their bodyweight. So, if you weigh 65kg you’ll need 65 micrograms of vitamin K each day.

You can learn more about vitamin K by reading our guide

What’s the best way to get vitamin K?

The best way to get vitamin K is through your diet. If you think you’re not getting enough, try introducing more green leafy vegetables like broccoli and spinach into your meals throughout the week.

In general, the NHS recommends having a diet that ticks all the following boxes:

  • At least five portions of varied fruits and vegetables each day
  • Plenty of high-fibre, wholegrain carbohydrates e.g. wholemeal bread
  • Small amounts of low-fat, low-sugar dairy e.g. milk, yoghurt
  • Healthy protein sources like pulses, eggs, oily fish, and lean meats
  • Less junk food that’s high in saturated fat, salt, and sugar
  • Less red meat and processed meat

If you can stick to these basic rules, you should be able to get all the essential nutrients you need, including vitamin K. Read our healthy eating guide for more advice.

What causes a vitamin K deficiency?

Vitamin K deficiency in adults

A vitamin K deficiency in healthy adults is unusual. However, it’s possible to develop one as a result of malnourishment – this is where you’re not eating enough foods that contain essential nutrients.

Another risk factor for vitamin K deficiency is the anticoagulant warfarin. This is a blood-thinning medication that’s given to people who have had blood clots, or who are at risk of clots in the future. Warfarin is known as a “vitamin K antagonist” because it essentially counteracts the effects of vitamin K, by reducing clotting.

Other risk factors for a deficiency include:

  • Having liver disease
  • Having biliary tract disease
  • Having an alcohol dependency
  • Having a condition that affects how well your body absorbs nutrients e.g. coeliac disease, Crohn’s disease
  • Receiving food intravenously (without vitamin K supplements)

Vitamin K deficiency in babies

Newborn babies are more susceptible to vitamin K deficiency than adults. Soon after birth they can present with a bleeding disorder known as vitamin K deficiency bleeding (VKDB).

VKDB can happen because the placenta isn’t transferring enough vitamin K to the baby in the womb. It might also occur after birth because the baby struggles to breastfeed, or because there’s not enough vitamin K in the mother’s breast milk.

Other risk factors for babies include:

  • Certain medications taken by the mother (e.g. anticoagulants)
  • Liver disease
  • Conditions that prevent the absorption of nutrients e.g. diarrhoea

What are the symptoms of a vitamin K deficiency?

In adults, a vitamin K deficiency tends to cause excessive bleeding. You might notice that you bleed a lot from a minor injury, and that the wound doesn’t heal as quickly as it should.

Bleeding might come in the form of nosebleeds, heavy periods, blood in the urine, or bleeding from the gums. Bleeding might also occur under the skin, causing severe bruising or petechiae – these are small red spots that appear on the skin, resembling a rash.

In babies, vitamin K deficiency also causes bleeding, which may occur internally or externally (e.g. from the umbilical stump after birth).

How is vitamin K deficiency treated?

A vitamin K deficiency can be treated (e.g. with injections of vitamin K) but your doctor may need to do a differential diagnosis – this is where they consider several different conditions that could be causing your symptoms.

The exact treatment will vary depending on what is causing the deficiency, and how severe the symptoms are. In some cases, the cause might be an underlying condition, and treatment will involve the management of this disease.


Do I need to take vitamin K supplements?

If you think you might have a vitamin K deficiency you should talk to your GP rather than simply taking vitamin K supplements.

Your GP may want to run some tests to work out what is causing the problem. They may be able to prescribe medication, or they may simply recommend getting more vitamin K in your diet.

Generally, healthy adults eating a varied and balanced diet should be able to get all the vitamin K they need. However, the NHS recommends that taking no more than 1mg of vitamin K supplements each day is unlikely to cause harm for most people.

If you’re going to try vitamin K supplements, you should talk to your GP beforehand. This is particularly important if you’re currently taking any medications like warfarin.