Vitamin K

Vitamin K plays a key role in helping the blood clot, preventing excessive bleeding.  Unlike many other vitamins, vitamin K is not typically used as a dietary supplement.

Vitamin K Uses

Low levels of vitamin K can raise the risk of uncontrolled bleeding.  While vitamin K deficiencies are rare in adults, they are very common in newborn infants.  A single injection of vitamin K for newborns is standard.  Vitamin K is also used to counteract an overdose of the blood thinner Coumadin.

While vitamin K deficiencies are uncommon, you may be at higher risk if you:

• Have a disease that affects absorption in the digestive tract, such as Crohn's disease or colitis
• Take drugs that interfere with vitamin K absorption
• Are severely malnourished
• Drink alcohol heavily

In these cases, a doctor might suggest vitamin K supplements. 

Vitamin K may help stop bone loss from osteoporosis.  However, it's not clear that supplements will help people with osteoporosis who don't also have a vitamin K deficiency.  Other uses of vitamin K -- for cancer, for the symptoms of morning sickness, for the removal of spider veins, and for other conditions -- are unproven.

Vitamin K Dose & Instructions for Use

The recommended dietary allowance (RDA) includes the total amount of vitamin K you take in, both from food and other sources.  Most people get enough vitamin K from their diets.

Group	Recommended Dietary Allowance
Children 0-6 months	5 micrograms/day
Children 6-12 months	10 micrograms/day
Children 1-3	15 micrograms/day
Children 4-6	20 micrograms/day
Children 7-10	30  micrograms/day
Children 11-14	45 micrograms/day
Girls 15-18	55 micrograms/day
Women 19-24	60 micrograms/day
Women 25 and up	65 micrograms/day
Women, pregnant or breastfeeding	65 micrograms/day
Boys 15-18	65 micrograms/day
Men 19-24	70 micrograms/day
Men 25 and up	80 micrograms/day

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Vitamin K is well-tolerated even at high doses.  Researchers have not set a maximum safe dose.

Vitamin K Food Sources

Good natural food sources of vitamin K include:

• Vegetables like spinach, asparagus, and broccoli
• Beans and soybeans
• Eggs
• Strawberries
• Meat

Vitamin K Supplement Information

Vitamin K is available in oral and topical forms.  Injectable vitamin K is only available by prescription.   Don't take vitamin K supplements without the guidance of your doctor.

Like any supplement, keep vitamin K supplements in a cool, dry place, away from humidity and direct sunlight. 

Vitamin K Warnings

• Side effects of vitamin K include upset stomach.  At higher doses, vitamin K may trigger allergic reactions. 
• Interactions.  Many drugs can interfere with the effects of vitamin K.  They include antacids, blood thinners, antibiotics, aspirin, and drugs for cancer, seizures, high cholesterol, and other conditions.
• Risks.  You should not use vitamin K supplements unless your doctor tells you to.  People using Coumadin for heart problems, clotting disorders, or other conditions may need to change their diets to control the amount of vitamin K they take in.