Who Should Not Use Ozone Therapy? Contraindications Explained

Some people should not have systemic ozone therapy. The Madrid Declaration on Ozone Therapy, 4th edition (ISCO3, 2025) lists 11 contraindications, including G6PD deficiency, toxic hyperthyroidism, very low platelets, severe heart instability and a recent heart attack [1].

This page paraphrases that list in plain words. It is education, not medical advice. Check with your healthcare provider before starting, especially if you are pregnant, have a heart or bleeding condition, or take blood thinners.

What does "systemic" mean?

Systemic means the ozone reaches the whole body: IV ozone (MAH), ozonized saline, and rectal or vaginal insufflation are in the Declaration's systemic group. Local or topical use works on one area, such as ozone oil on the skin. The list below is written for systemic use. If you are unsure which applies to you, ask your provider.

Who should not use systemic ozone therapy?

The Declaration says ozone is contraindicated, meaning it should not be used, in these cases [1]:

1. Breathing ozone gas directly. The fluid lining the lungs has no antioxidants, so inhaled ozone is toxic. See why you can’t breathe ozone.
2. G6PD deficiency (debated, see below). This is an inherited enzyme condition (favism) that can lead to acute hemolytic anemia, where red blood cells break down.
3. Toxic hyperthyroidism. This means severe Graves' disease.
4. Low platelets and severe clotting disorders. A platelet count under 50,000 is on the list.
5. Severe cardiovascular instability.
6. Acute alcohol intoxication.
7. A recent heart attack.
8. Acute massive bleeding.
9. During seizures. The Declaration says convulsive states.
10. Hemochromatosis. This is a condition where the body stores too much iron.
11. People receiving intravenous copper or iron therapy.

Do I need a G6PD test?

Whether G6PD deficiency is an absolute contraindication is debated. The Declaration lists it as one and recommends G6PD testing before ozone therapy [1]. It cites a published report on hemolytic anemia in G6PD deficiency in connection with ozone therapy [2].

In everyday clinical practice, most ozone physicians do not treat it as absolute, and many experienced ozone physicians do not routinely test for it. G6PD deficiency means lower antioxidant capacity. Ozone works by giving the body a small, controlled oxidative stress that it responds to, so a person with low antioxidant capacity may get less benefit and more stress. That is why the protocol matters: start low, below the person's antioxidant capacity, go slow, build up over time, and have the physician monitor the patient. On our protocols, G6PD deficiency sits under considerations for standard IV ozone, and it is an absolute contraindication for 10-Pass, EBOO and HiDose.

Keep in mind that the Madrid Declaration is written as a consensus to help bring ozone therapy into mainstream medicine, an effort that has had some success in European countries. For that reason it takes the strictest position on safety questions. Talk to your physician about whether testing makes sense for you.

What other cautions does the Declaration give?

• Blood thinners. Giving ozone together with some anticoagulants can change clotting, so the INR needs frequent monitoring. The Declaration says the newer direct oral anticoagulants (rivaroxaban, dabigatran, apixaban and edoxaban) are compatible with ozone and need no INR monitoring.
• Combining oxidant therapies. It advises against stacking two or more bio-oxidative therapies in the same session, such as mega-dose vitamin C and ozone.

Warning: pregnancy

The Declaration puts pregnancy in a separate warning section (2.2), not in the contraindication list above [1]. It says ozone therapy has been used with good results for conditions linked to pregnancy, such as gestosis, placental insufficiency, slowed fetal growth, cervical ectopia and preeclampsia. However, it should be avoided during the first trimester (weeks 0 to 13), a critical time for the development of the embryo and fetus. Use in obstetrics and gynecology is for specialists in that field. Our IV protocol lists pregnancy as an absolute contraindication.

Check with your healthcare provider before starting if you are pregnant or could be.

The IV protocol also lists its own contraindications, adapted from the Declaration: see the IV protocol contraindications. For the wider safety picture, see the safety of ozone therapy and ozone therapy side effects.

Frequently asked questions

Who should not have ozone therapy?

People with G6PD deficiency (whether this is absolute is debated), toxic hyperthyroidism, platelets under 50,000 or severe clotting disorders, severe cardiovascular instability, acute alcohol intoxication, a recent heart attack, acute massive bleeding, seizures, hemochromatosis, or who are receiving IV copper or iron. Nobody should breathe ozone gas.

Can I do ozone therapy if I take blood thinners?

Talk to your provider first. Ozone can change clotting with some anticoagulants, so monitoring is needed. The Madrid Declaration says the newer direct oral anticoagulants are compatible and need no INR monitoring.

Is ozone therapy safe in pregnancy?

The Madrid Declaration warns to avoid it in the first trimester and to leave obstetric use to specialists. Check with your healthcare provider before starting if you are pregnant.

What is G6PD deficiency and why does it matter?

It is an inherited enzyme condition that protects red blood cells from oxidative stress. Without enough of the enzyme, red blood cells can break down. The Declaration lists it as a contraindication and recommends testing before ozone therapy. In practice many ozone physicians treat it as a reason to start low and monitor rather than an absolute bar. Talk to your physician.

Do these contraindications apply to ozone oil on the skin?

The Declaration writes the list for systemic use. Ozone oil on the skin acts on one area, but if you have any condition on this list, ask your provider before using any ozone product.

Sources

1. ISCO3. Madrid Declaration on Ozone Therapy, 4th edition (ISCO3, 2025). Sections 2.1 to 2.6 and 16. isco3.org
2. González Sánchez E, et al. Hemolytic anemia due to G6PDH deficiency. About ozone therapy. Ozone Therapy Global Journal. 2019;9(1):87-102.