Supplements›Heart & blood sugar

Nattokinase: who should take it, and how

Nattokinase is a natto enzyme for people concerned about circulation or blood pressure. The standard approach is 2,000 FU a day on an empty stomach. But if you take a blood thinner like aspirin or warfarin, don't combine them because of the bleeding risk.

Who it’s for

People with poor circulation and cold hands and feet, or slightly high blood pressure

Daily dose

2,000 FU a day is standard (range 2,000–6,000 FU)

When

Empty stomach (1 hour before a meal or 2 hours after)

Best form

Patented NSK-SD ingredient, with FU listed on the label

What is nattokinase?

Nattokinase is an enzyme extracted from natto, a Japanese fermented soybean food. Enzymes are proteins that break substances down into smaller pieces.

What nattokinase breaks down is blood clots (clumps formed when blood sticks together). It can dissolve clots directly, and it can also help by switching on your body's own clot-dissolving system (plasmin). That's how it earned the nickname "blood vessel cleaner."

Nattokinase benefits: how much can you expect?

BenefitStrength of evidence
Breaks down clots, keeps blood flowingThe effect is fairly clear. When healthy men took 2,000 FU, their blood took longer to clot.
Blood pressureWhen 86 people with slightly high blood pressure took it for 8 weeks, their systolic (top number) pressure dropped by about 5.5 on average. It's also been officially recognized as a blood pressure ingredient in some countries.
Cholesterol and LDL ("bad") cholesterolSome data show decreases, but the evidence is still weak.
DementiaNot enough evidence.
To be honest, most of the research is in test tubes and animals, and there are only a few human studies. Rather than expecting too much, think of it as a small boost on top of healthy habits.

Who it may help

  • □ Your hands and feet are cold and your circulation is poor
  • □ Your blood pressure runs slightly above normal
  • □ The veins in your legs bulge and your legs tend to swell (varicose veins)
  • □ You're concerned about your cholesterol numbers
If you already have a blocked blood vessel and are being treated, or you take clot medication, don't decide on your own — always talk to your doctor. Nattokinase can't replace medication.

Who should not take nattokinase

  • People taking blood thinners like aspirin or warfarin — The bleeding risk goes up. There's even a case of tiny bleeds in the brain after taking it with aspirin.
  • People with conditions where bleeding is hard to stop, such as hemophilia
  • People with ulcers, such as stomach ulcers or ulcerative colitis — The sore areas may bleed.
  • Pregnant women
  • People with naturally low blood pressure — If you feel dizzy or get a headache after taking it, stop right away.
  • People with a soy allergy
  • People with upcoming surgery or dental procedures — Stop at least 2 weeks before.

Also, if you eat 20–30 g of natto every day, you don't need a separate supplement.

When and how much nattokinase to take

Bottom line: 2,000 FU a day, on an empty stomach.

  1. Look at the dose in FU. FU is a unit that shows how active the enzyme is. FU matters more than mg. The amount used most often in studies is 2,000 FU a day.
  2. Take it on an empty stomach. Enzymes are proteins, so stomach acid can break them down. And if you take it with food, it gets used up breaking down food protein instead of clots.
  3. If needed, split it into 1–2 doses a day. The range is 2,000–6,000 FU.
Good pairings: There's data showing it did a better job preventing clots when taken with Pycnogenol. It's also sometimes combined with red yeast rice.

How to choose nattokinase

  1. Is it the NSK-SD ingredient? — It's a patented Japanese ingredient, and most good products use it.
  2. Is the FU amount listed? — If it only lists mg and no FU, you can't tell how active the enzyme is.
  3. Has vitamin K2 been removed? — Natto naturally contains vitamin K2. K2 plays a role in blood clotting, so products with it removed are cleaner.
  4. Check that it's from a well-managed company.

Medications and conditions to watch

  • Caution Antithrombotic drugs like warfarin and aspirin — Higher bleeding risk; a case of tiny bleeds after taking it with aspirin — don't take them together

Combinations

Works well with: Pycnogenol, Red yeast rice

Frequently asked questions

When should I take nattokinase?

Take it on an empty stomach. One hour before a meal or 2 hours after is best. If you take it with food, the enzyme gets used up breaking down food protein.

Can I take nattokinase with aspirin?

No. Both thin the blood, so the bleeding risk goes up. There's even a case of tiny bleeds in the brain after taking them together.

How many FU of nattokinase should I take a day?

2,000 FU a day is standard. It's also the dose used most often in studies. The range is 2,000–6,000 FU.

Should I stop nattokinase before surgery?

Yes, stop at least 2 weeks before. Your blood may not clot well. The same goes for procedures like a tooth extraction.

If I eat natto, do I still need a nattokinase supplement?

If you eat 20–30 g of natto every day, you don't need a separate supplement.

Does nattokinase lower blood pressure?

In one study, people with slightly high blood pressure who took it for 8 weeks saw their systolic (top number) pressure drop by about 5.5 on average. But it can't replace blood pressure medication, so keep taking your medication.

Related concerns

High blood pressureHigh cholesterolSwelling & cold hands and feet

Last updated 2026-10-12