Although garlic is a familiar food with a long history of use, its concentrated extract acts differently from the small amount found in a dish.
- Anticoagulants and medicines that affect blood clotting. Garlic's sulfur-containing compounds may enhance the effect of such medicines. If you take warfarin, aspirin at therapeutic doses or similar medicines, be sure to check with your doctor whether the supplement is compatible with your treatment regimen.
- A sensitive stomach and gastrointestinal conditions. The oil capsule form is gentler than raw garlic, but with gastritis, an ulcer or reflux even the extract can cause discomfort. In such cases, it is best to agree on taking it with a specialist and not to take the supplement on an empty stomach.
- Pregnancy, breastfeeding, childhood and allergies. According to the label, the supplement is not suitable for children or for pregnant and breastfeeding women; it is also not used by people who are allergic to garlic or to other ingredients of the capsule.
- Upcoming surgery. Because of the possible effect on blood clotting, it is recommended to stop taking garlic supplements one to two weeks before planned surgery — this, too, is decided together with your doctor.
In all other cases, the supplement is regarded as a standard herbal addition to the diet, not as a medicine.