Grapes are not high in vitamin K. A cup of fresh grapes, whether red or green, supplies roughly 14 to 22 micrograms of vitamin K, which is a small fraction of the 90 to 120 micrograms most adults need daily. That puts grapes far below the leafy greens and cruciferous vegetables that dominate vitamin K rankings. Yet grapes still show up in questions about this nutrient, partly because people on blood-thinning medications worry about every food on their plate, and partly because the relationship between grapes and clotting turns out to be more complicated than vitamin K content alone would suggest.
How Much Vitamin K Is Actually in Grapes
A one-cup serving of raw grapes, roughly 150 grams, contains somewhere in the neighborhood of 14 to 22 micrograms of vitamin K depending on the variety. Red and green table grapes fall in the same general range. To put that in perspective, the same-sized serving of raw spinach delivers about 145 micrograms, a cup of chopped kale around 550 micrograms, and a cup of broccoli about 90 micrograms. The gap between grapes and these leafy and cruciferous vegetables is enormous. You would need to eat five or six cups of grapes just to match the vitamin K in one cup of broccoli.
The form of vitamin K in grapes is phylloquinone, also called vitamin K1. This is the form found in virtually all plant foods, synthesized in chloroplasts as part of the photosynthetic machinery. Animals and certain bacteria produce a different family of the vitamin, the menaquinones (collectively called vitamin K2), but plants stick to K1. Since grapes grow on vines with abundant green leaves but the fruit itself has comparatively little chlorophyll, the vitamin K content of the edible berry is modest. The leaves of the grapevine, which are eaten in some cuisines, carry more.
Grape Products Compared
When people ask about grapes and vitamin K, they often mean more than just fresh table grapes. Raisins, grape juice, wine, and grape seed oil are all part of the picture, and their vitamin K content varies.
- Raisins: Drying concentrates some nutrients, but vitamin K in raisins remains low. A small box of raisins provides only a few micrograms.
- Grape juice: Commercial grape juice retains a small amount of vitamin K from the whole fruit, generally in the range of 5 to 10 micrograms per cup. Filtering and processing reduce it further.
- Wine: A standard glass of red or white wine contains a negligible amount of vitamin K, typically under 5 micrograms. The fermentation process does not meaningfully boost it.
- Grape seed oil: Oils from seeds can sometimes be significant vitamin K sources, as seen with soybean oil and canola oil, but grape seed oil is relatively low. It does not come close to the 25 micrograms per tablespoon found in soybean oil.
None of these grape-derived products would be classified as a meaningful source of vitamin K in a dietary assessment. If your goal is to increase your vitamin K intake, green leafy vegetables, certain vegetable oils, and fermented foods like natto are far more efficient.
Why People on Blood Thinners Still Ask About Grapes
The vitamin K question almost always connects back to warfarin, the anticoagulant medication that works by interfering with the vitamin K cycle in the liver. People prescribed warfarin are told to keep their vitamin K intake consistent from day to day, because large swings can push their clotting levels out of range. This advice leads many patients to scrutinize every fruit and vegetable, even those with only trace amounts of the vitamin.
With grapes specifically, the concern is understandable but slightly misplaced. At 14 to 22 micrograms per cup, fresh grapes are unlikely to destabilize anyone’s warfarin therapy unless consumed in truly unusual quantities. The real issue with grapes and anticoagulation, when it arises, involves a different mechanism entirely. A published case report described a 73-year-old woman on warfarin whose clotting values climbed to dangerous levels after she ate scuppernongs, a variety of muscadine grape, regularly over two months. The investigators attributed the interaction not to vitamin K but to quercetin, a flavonoid abundant in muscadine grapes, which can inhibit the enzyme that metabolizes warfarin and amplify the drug’s effect.1PubMed Central. Clinically relevant interaction between warfarin and scuppernongs, a quercetin containing muscadine grape: continued questions surrounding flavonoid-induced warfarin interactions
That case is worth knowing about because it illustrates a broader point: fruit and vegetable interactions with warfarin are not exclusively about vitamin K. Flavonoids, grapefruit compounds, and other plant chemicals can alter drug metabolism through entirely separate pathways. A grape might be innocuous on the vitamin K front but still relevant for someone on certain medications if consumed in large, sustained quantities. If you take warfarin and eat grapes regularly, the key is the same advice that applies to everything else: keep your intake consistent and report any major dietary changes to your healthcare provider.
Where Grapes Rank Among Common Fruits
Among fruits, grapes are middling when it comes to vitamin K. Most fruits are not significant sources. Blueberries tend to rank near the top of the fruit category with roughly 28 micrograms per cup, followed by grapes and kiwifruit. Citrus fruits like oranges and grapefruit carry less, usually under 5 micrograms per serving. Bananas and apples hover in the same low range. The standout in the broader fruit world is prunes, which can deliver around 50 to 60 micrograms per cup.
The reason fruits as a group are low in vitamin K goes back to where plants store phylloquinone. It is concentrated in photosynthetic tissue: leaves, stems, and green outer parts of vegetables. Fruit flesh, which exists primarily to attract animals that spread seeds, is packed with sugars, water, and certain antioxidants but has little need for the photosynthetic pigments and electron carriers that accompany vitamin K1. The greener a vegetable or fruit is, the more phylloquinone it generally contains. That is why a head of romaine lettuce far outpaces a bunch of grapes.
The Two Forms of Vitamin K and What Your Body Does With Them
Vitamin K comes in two main families. Phylloquinone (K1) is the plant-derived form, and menaquinones (K2) are produced by bacteria and are also found in animal-based and fermented foods. The K2 family is itself a collection of related molecules with varying side-chain lengths, but the one that gets the most attention is MK-4, partly because the body can convert dietary K1 into MK-4 in certain tissues. Research in animal models has confirmed that dietary phylloquinone serves as a precursor for MK-4 in organs like the brain, kidney, and reproductive tissues, and that different tissues accumulate the two forms selectively.2PubMed. Vitamin K distribution in rat tissues: dietary phylloquinone is a source of tissue menaquinone-4
This conversion matters because it means the K1 you get from grapes and other plant foods is not limited to one biological role. The liver uses K1 directly to activate clotting factors, but other tissues may convert it to MK-4 for local functions. Whether grapes contribute meaningfully to that conversion is questionable given how little K1 they provide, but the point is that the small amount of K1 in your overall diet feeds into a bigger system than just blood clotting.
Vitamin K Beyond Clotting
Blood clotting is the best-known role of vitamin K, but researchers have been steadily mapping out other functions. One of the most studied is the vitamin’s involvement in vascular health. A protein called matrix Gla protein, or MGP, acts as a powerful inhibitor of calcium buildup in blood vessel walls. MGP needs vitamin K to become fully activated through a chemical modification called carboxylation. Without enough vitamin K, MGP remains inactive, and calcium can accumulate in arteries, contributing to stiffness and cardiovascular risk.3PubMed Central. The Inhibitory Roles of Vitamin K in Progression of Vascular Calcification
Clinical research has explored whether supplementing vitamin K can improve this picture, particularly in people at high risk for vascular calcification such as dialysis patients. A randomized trial comparing vitamin K2 to K1 supplementation in hemodialysis patients found that K2 produced a much larger increase in activated MGP levels than K1 did, suggesting the two forms are not interchangeable for this particular function.4Nephrology Dialysis Transplantation. MO789: The Effect of Oral Vitamin K2 Versus K1 on Vascular Calcification in Hemodialysis Patients: A Randomized Controlled Trial These findings don’t directly relate to grape consumption, since grapes are not a rich source of either form, but they do help explain why nutritionists and cardiologists pay attention to vitamin K intake beyond what clotting alone would demand.
Vitamin K has also been linked to bone metabolism. It activates osteocalcin, a protein involved in binding calcium into the bone matrix. Population studies have associated higher vitamin K intake with better bone mineral density and lower fracture rates, particularly in older adults. Again, grapes won’t move the needle here on their own, but they contribute in a small way to total dietary K1 alongside the leafy greens that do the heavy lifting.
Common Misconceptions About Vitamin K in Foods
One persistent misunderstanding is that all fruits and vegetables are dangerous for people on warfarin. In reality, only a handful of foods are concentrated enough in vitamin K to cause problems if intake swings dramatically. A person who eats a steady amount of leafy greens each week is at far lower risk of clotting instability than someone who avoids greens entirely for weeks and then eats a large salad. Grapes sit in the comfortable zone for warfarin patients: low enough in vitamin K that normal portions are a nonissue, as long as you’re not radically changing the amount you eat from one week to the next.
Another misconception is that “vitamin K” is a single substance. As described earlier, it spans a family of compounds with different sources and, to some extent, different biological roles. The K1 in grapes and the K2 in fermented cheese are structurally and functionally distinct. Lumping them together can lead to confusion, especially when supplement labels market K2 for bone or cardiovascular health while dietary guidelines focus primarily on K1 from plant foods. For general healthy eating, getting enough vitamin K from a varied diet that includes green vegetables is the simplest approach. Supplements are a separate conversation, most relevant for people with specific absorption problems or medical conditions.
Getting Enough Vitamin K From Food
The adequate intake for vitamin K is set at 120 micrograms per day for adult men and 90 micrograms per day for adult women in the United States. These values are not hard thresholds for deficiency; they represent intake levels considered sufficient for normal clotting function in most people. True vitamin K deficiency in healthy adults is rare, because the vitamin is widespread in the food supply and the body recycles it efficiently.
That said, some groups are more vulnerable to low intake. People with fat malabsorption conditions, those on prolonged courses of broad-spectrum antibiotics (which can disrupt gut bacteria that produce some K2), and newborns (who have very low vitamin K stores at birth) are the classic at-risk populations. For everyone else, a diet that includes at least one serving of green vegetables a day typically provides more than enough. Grapes can be part of that dietary pattern, contributing their small share alongside more concentrated sources.
If you are trying to track your vitamin K intake, the USDA nutrient database is the most reliable public resource for food composition data in the United States. When reading food labels, keep in mind that vitamin K is not required to appear on the Nutrition Facts panel, so the absence of a listing does not mean a food lacks it. It means the manufacturer chose not to include the information.
Grape Polyphenols and Their Separate Health Story
Grapes get far more scientific attention for their polyphenol content than for their vitamin K. Resveratrol, anthocyanins, quercetin, and proanthocyanidins are the compounds that drive most grape-related health research, covering topics from heart health to inflammation to cancer biology. These polyphenols have nothing to do with vitamin K biochemically, but they sometimes get tangled up in the same conversations because both touch on cardiovascular health.
The quercetin angle is worth revisiting here. As the warfarin case report illustrated, quercetin in muscadine grapes interfered with drug metabolism through a pathway unrelated to vitamin K.1PubMed Central. Clinically relevant interaction between warfarin and scuppernongs, a quercetin containing muscadine grape: continued questions surrounding flavonoid-induced warfarin interactions This kind of overlap between nutrient questions and phytochemical questions happens a lot with grapes. Someone researching “grapes and blood thinners” might assume vitamin K is the culprit, when the actual concern could be a flavonoid interaction, or even the antiplatelet effects that some grape compounds have been shown to exert in laboratory studies. The bottom line for grape lovers is that the fruit is nutritionally harmless with respect to vitamin K in normal servings, but its broader chemistry is more complex than a simple nutrient label suggests.
For people not on anticoagulant medications, none of these interactions are clinically meaningful at normal dietary intakes. Grapes remain one of the safer, more benign fruits from a drug-interaction standpoint. Their vitamin K content is too low to worry about, their polyphenol content is generally viewed as beneficial, and the edge cases that show up in medical case reports involve unusual quantities or specific grape varieties consumed over extended periods.