Vitamins K and A do not get the spotlight that C and D enjoy, but both are essential, and both come with safety points worth understanding. They are fat-soluble vitamins, which means the body can store them — and that storage is exactly why a little knowledge helps.
This guide covers what each does, where to find them, and the deficiency and caution patterns people search for.
Vitamin K: clotting and bone
Vitamin K is best known for its role in blood clotting, and it also contributes to bone health. There are two main types: K1, found in leafy green vegetables, and K2, found in some animal and fermented foods. True dietary deficiency is uncommon in healthy adults, but newborns are routinely given vitamin K because they are born with very little.
Vitamin A: vision, skin, and immunity
Vitamin A supports vision (especially in low light), skin, and the immune system. It comes in two dietary forms: preformed vitamin A from animal foods like liver, eggs, and dairy, and provitamin A carotenoids such as beta-carotene from colourful plants like carrots, sweet potatoes, and leafy greens, which the body converts as needed.
The safety side of fat-soluble vitamins
- Because A and K are stored rather than flushed out, high-dose supplements carry more risk than water-soluble vitamins.
- Too much preformed vitamin A can be harmful, and is especially a concern in pregnancy — this is a clear talk-to-your-provider situation.
- Beta-carotene from food is handled differently and does not carry the same toxicity risk.
- More is not better with either vitamin.
Deficiency patterns people search for
- Vitamin K shortfalls are more likely with certain gut or liver conditions, or fat-absorption problems.
- Vitamin A deficiency is rare in well-fed populations but a major issue globally; early signs can include difficulty seeing in dim light.
- Both are more relevant for people with conditions that impair fat absorption.
What to ask your provider
- If you take blood thinners, how vitamin K fits with your medication.
- Whether a supplement is appropriate for you, given the storage and safety issues.
- In pregnancy, what is safe regarding vitamin A specifically.
- Whether any digestive condition you have affects these fat-soluble vitamins.
Common questions
What does vitamin K do?
It is essential for blood clotting and contributes to bone health. It also interacts with blood-thinning medication, which is its most important practical point.
Can you take too much vitamin A?
Yes. Because it is stored in the body, high-dose preformed vitamin A can be harmful and is a particular concern in pregnancy. Beta-carotene from food does not carry the same risk.
Where do you get vitamins K and A?
Vitamin K from leafy greens and some fermented or animal foods; vitamin A from animal foods and from colourful plants via beta-carotene.
K and A are quiet essentials with real safety footnotes. Food usually has you covered — and if a supplement or a medication is in the picture, that is a provider conversation.
Our Vitamins & Minerals guides break down topics like this one in plain English — what each nutrient does, who tends to run low, and the questions worth asking your provider — so you can walk into your next appointment prepared.
Explore the Vitamins & Minerals guides →