Nattokinase Safety: Medicines, Surgery and Who Should Avoid It

July 23, 2026|Barry Lees

Nattokinase Complex supplement — nattokinase safety guide, who should not take it

Direct answer: Nattokinase may not be appropriate for people taking anticoagulant, antiplatelet or blood-pressure medicines; people with a bleeding or clotting disorder; anyone with planned surgery or an invasive dental procedure; or people who are pregnant or breastfeeding. Product warnings differ, so read the complete label and ask a doctor or pharmacist before use. Never replace prescribed medication with nattokinase.

Commercial disclosure: The Health Improvers sells Nattokinase Complex. This safety guide is deliberately cautious and should be read before the product page.

Who should avoid nattokinase or obtain professional advice first?

Situation	What to do
Anticoagulant medicine	Do not add nattokinase without advice from the clinician or pharmacist managing your treatment.
Antiplatelet medicine or regular aspirin	Ask a doctor or pharmacist before use because combined effects may increase bleeding risk.
Blood-pressure medicine	Follow the product warning and check with your prescriber or pharmacist first.
Bleeding or clotting disorder, previous haemorrhage or easy unexplained bleeding	Do not self-select nattokinase; obtain medical advice.
Surgery, endoscopy or invasive dental treatment	Tell the procedure team about every supplement you take and follow their individual instructions.
Pregnancy or breastfeeding	Avoid unless an appropriate healthcare professional specifically advises otherwise; safety evidence is inadequate.
Soy allergy	Do not use a product that declares soy.
Under 18	Do not use an adult supplement unless a qualified professional recommends it.

Why are blood-thinning medicines a concern?

Nattokinase is studied because of its fibrinolytic activity. That laboratory property is also the reason for caution around medicines and conditions that affect bleeding or clotting.

A published case report described a cerebellar haemorrhage in a person taking aspirin who added nattokinase and already had cerebral microbleeds. A single case cannot quantify the risk for everyone, but it supports avoiding casual combination with antithrombotic treatment.

NHS guidance advises anyone taking anticoagulants to speak to their GP, anticoagulant clinic or pharmacist before taking another medicine, remedy or supplement.

Never use nattokinase instead of prescribed anticoagulation

Nattokinase is a food supplement, not an approved substitute for warfarin, apixaban, rivaroxaban, dabigatran, edoxaban, clopidogrel or prescribed aspirin.

A case report documented thrombosis on a mechanical heart valve after a patient replaced warfarin with nattokinase. The authors strongly discouraged using nattokinase for that purpose. Do not stop, reduce or replace prescribed medicine without the clinician responsible for your treatment.

What should you do before surgery or dental treatment?

Tell the surgeon, anaesthetist, dentist or pre-assessment team that you take nattokinase. Do this early enough for them to assess your procedure and personal risks.

There is no universal evidence-based stopping period that a supplement seller should prescribe for every procedure. Follow the timing given by your procedure team, and do not alter prescribed anticoagulant or antiplatelet medication yourself.

Pregnancy and breastfeeding

There is not enough reliable human safety evidence to recommend nattokinase during pregnancy or breastfeeding. Our current product label says it should not be taken during pregnancy. Breastfeeding customers should seek professional advice and choose another option unless specifically advised otherwise.

What about blood-pressure medication?

Some small studies have examined nattokinase and blood-pressure outcomes, while a larger long-term randomized trial found no significant blood-pressure effect. That uncertainty is not a reason to combine it with prescribed treatment without checking. Our product warning says not to take it with blood-pressure medication.

Possible warning signs

Stop taking the supplement and seek prompt medical advice if you develop unusual or persistent bleeding, unexplained heavy bruising, blood in urine or stool, or another concerning reaction. Severe bleeding, sudden weakness, difficulty speaking, collapse or a sudden severe headache requires urgent emergency help—call 999.

How to discuss nattokinase with a pharmacist

Take the complete product label or a clear photograph and tell the pharmacist:

every prescription medicine you take;
regular over-the-counter medicines, especially aspirin or anti-inflammatory painkillers;
other supplements and herbal products;
any history of bleeding, clotting, stroke, heart-valve treatment or low blood pressure;
any planned operation, endoscopy or dental procedure.

This is more useful than asking whether nattokinase is “generally safe”, because suitability depends on the person, product and complete medication list.

Our product’s current directions and cautions

The Health Improvers Nattokinase Complex directs adults to take one capsule daily with water. It declares soy and says it should not be taken with blood-pressure or blood-thinning medication or during pregnancy. The full label and How to take it section should be checked before ordering.

Frequently asked questions

Can I take nattokinase with warfarin or a DOAC?

Do not add it without explicit advice from your anticoagulant clinic, doctor or pharmacist. Never alter your prescribed dose yourself.

Can I take nattokinase with aspirin?

Regular aspirin may be prescribed as an antiplatelet medicine. Ask the prescriber or pharmacist before combining it with nattokinase.

How long before surgery should I stop nattokinase?

Ask the procedure team. The appropriate plan depends on the procedure, your medical history and your other medicines; a supplement seller should not give everyone the same stopping period.

Is nattokinase safe for healthy adults?

Available studies do not establish safety for every adult, every formulation or long-term self-treatment. Check the label, medication interactions, allergies and personal circumstances before use.

Does natto food have the same cautions?

Natto is a whole food and can contain vitamin K, which is particularly relevant to warfarin. A nattokinase supplement is a concentrated enzyme preparation. Anyone taking an anticoagulant should discuss both dietary changes and supplements with their clinical team.

How this guide was checked

This page was reviewed on 3 August 2026 using the current Health Improvers product information, NHS anticoagulant guidance, published case reports and the available randomized human trial. It provides general safety information and cannot assess an individual medication list.

Sources

For composition and label comparison, read What Is Nattokinase? and the UK nattokinase comparison guide.

This article is general information, not medical advice. Always read the label. Food supplements are not a substitute for a varied and balanced diet and a healthy lifestyle. If you think you may be having a serious adverse reaction, seek urgent medical help.