Vitamin K is the name of a family of compounds with a similar structure.

Vitamin K3, also known as menadione, is a synthetic or artificially produced form of vitamin K.

This article explains everything you need to know about vitamin K3, including its benefits, uses, and potential side effects.

Vitamin K is important for blood clotting and bone health. It may also prevent dangerous buildup of calcium in tissues, organs, and blood vessels of people with or at risk of certain conditions like kidney disease, heart disease, and diabetes (1, 2, 3).

Vitamin K3 is a synthetic, artificially produced form of vitamin K that doesn’t occur naturally. This is unlike the other two forms of vitamin K — vitamin K1, known as phylloquinone, and vitamin K2, called menaquinone.

Vitamin K3 may be converted into K2 in your liver. Many animals can also convert vitamin K3 to the active forms of vitamin K (4).

Though vitamin K3 isn’t legally sold in supplement form for humans due to safety concerns, it’s commonly used in poultry and pig feed, as well as commercial pet foods for dogs and cats (5).


Vitamin K3 is a synthetic form of vitamin K, commonly used in livestock and pet feed. It’s not used in dietary supplements for humans.

Research from the 1980s and 1990s has demonstrated that vitamin K3 is harmful to humans.

These studies have linked vitamin K3 to liver damage and the destruction of oxygen-carrying red blood cells (6).

For this reason, only the K1 and K2 forms of vitamin K are available as dietary supplements and prescriptions.

Despite the harmful effects of vitamin K3 in humans, the vitamin hasn’t demonstrated harm to livestock or pets when added to feed in regulated doses (6, 7).

Still, there’s controversy over whether K3 should be allowed in pet foods, with some companies who don’t add it claiming product superiority over companies who do.

In either case, the natural forms of vitamin K — K1 and K2 — have only low potential for toxicity in humans.

As such, the National Academy of Sciences and the European Food Safety Authority (EFSA) have not established an upper limit for vitamin K. An upper limit is the highest amount of a nutrient consumed likely to pose no harmful effects for most people (6, 8).


Vitamin K3 has been shown to be harmful to humans. However, the natural forms of vitamin K — K1 and K2 — have only a low potential for toxicity.

Despite its harmful effects in humans, vitamin K3 has demonstrated anticancer and anti-inflammatory properties in test-tube studies.

One test-tube study found that it killed human breast, colorectal, and kidney cancer cells by activating a special class of proteins (9, 10, 11).

The vitamin has also been shown to increase the production of reactive oxygen species, which are molecules that can damage or kill cancer cells (12, 13, 14, 15).

What’s more, some test-tube research suggests that vitamin C and vitamin K3 work synergistically to inhibit the growth of and kill human breast and prostate cancer cells (16).

In addition to these anticancer properties, the vitamin may also provide antibacterial effects.

One test-tube study showed that vitamin K3 inhibited the growth of Helicobacter pylori — a harmful type of bacteria that grows in the digestive tract — in infected human stomach cells, by decreasing the bacteria’s ability to replicate (17).

Although promising, more research is needed before any conclusions can be made about the safety or effectiveness of vitamin K3 for treating cancer or other conditions in humans.

Plus, because vitamin K3 has been shown to cause harm in humans, any possible future research will also need to consider whether the potential benefits of the vitamin for these conditions outweigh the risks.


Vitamin K3 has been shown to have anticancer and antibacterial properties in test-tube studies. However, these benefits have yet to be demonstrated in humans.

The National Academy of Sciences recommends that adult women consume 90 mcg per day of vitamin K and men 120 mcg (6).

On the other hand, EFSA recommends just 70 mcg for adults or 0.5 mcg per pound (1 mcg per kg) of body weight per day (18).

These recommendations are based on the minimum vitamin K intake needed to prevent deficiency signs (bleeding). More research is needed to determine the ideal amount of vitamin K to optimize bone health and prevent vascular calcification.

Because vitamin K is found in a variety of foods, most people can get enough through their diet.

Dietary sources of the natural forms of vitamin K

Vitamin K1 is found naturally in green leafy vegetables, including collards, spinach, kale, and broccoli, as well as vegetable oils like soybean and canola oil. Some fruits like blueberries and grapes also contain the vitamin.

Vitamin K2 is found mainly in fermented foods like sauerkraut and natto — a traditional Japanese dish made from fermented soybeans — but also in poultry and pork products. This form is also produced by bacteria in your digestive tract (19).

Good sources of vitamin K include (19):

  • 3 ounces (85 grams) of natto: 708% of the Daily Value (DV)
  • 1/2 cup (18 grams) of collards: 442% of the DV
  • 1/2 cup (45 grams) of turnip greens: 335% of the DV
  • 1 cup (28 grams) of spinach: 121% of the DV
  • 1 cup (21 grams) of kale: 94% of the DV
  • 1/2 cup (44 grams) of broccoli: 92% of the DV
  • 1 tablespoon (14 mL) of soybean oil: 21% of the DV
  • 3/4 cup (175 mL) of pomegranate juice: 16% of the DV
  • 1/2 cup (70 grams) of blueberries: 12% of the DV
  • 3 ounces (84 grams) of chicken breast: 11% of the DV
  • 1 cup (35 grams) of lettuce: 12% of the DV

How well vitamin K is absorbed depends on the source.

For example, the vitamin K in green leafy vegetables is tightly bound to plant cell organelles called chloroplasts. This makes it harder for your body to absorb compared with vitamin K from oils or supplements (20).

Nonetheless, green leafy vegetables tend to be the predominant source of vitamin K in American diets. You can increase the absorption of the vitamin from green leafy vegetables by eating them with fats like oil, nuts, or avocado (6).

Because vitamin K can interfere with the effectiveness of blood-thinning medications like Warfarin or Coumadin, make sure to talk with your physician before taking these supplements or increasing your intake of vitamin-K-rich foods.

That said, you don’t need to restrict or completely avoid vitamin-K-rich foods. Instead, keep your intake of those foods consistent (19).


Most people can get the recommended amounts of vitamin K through their diet. The best sources of vitamin K are green leafy vegetables and certain fermented foods like natto.

Vitamin K plays an important role in blood clotting, bone health, and maintaining healthy levels of calcium in your blood.

Vitamin K3 is a synthetic form of vitamin K, while vitamins K1 and K2 occur naturally.

Although vitamin K3 has demonstrated anticancer and antibacterial properties in test-tube studies, it has been shown to cause harm in humans. For this reason, it’s not sold as a supplement and isn’t available as a prescription, unlike vitamins K1 and K2.

In either case, most people get plenty of vitamin K through their diets, making it unnecessary to supplement with the vitamin.