Who Shouldn't Take Garlic?

Garlic, a pungent-smelling root vegetable closely related to onion and leek, has been used for thousands of years as both a food and medicine. Garlic offers a variety of important health benefits. It can reduce cholesterol, improve blood pressure, prevent blood clots and prevent many forms of cancer. In general, garlic is very safe and associated with few or no serious side effects.

However, there are a few garlic contraindications, or situations in which the use of garlic could be inadvisable. Garlic can cause serious adverse reactions in these susceptible individuals. Do not use garlic if you are in any of the following high-risk groups.

Pregnant Women

Although the amount of garlic found in food is perfectly safe for expectant mothers, supplements containing medicinal doses of garlic may be dangerous. No studies have evaluated garlic's effects on pregnancy, and it could theoretically increase the risk of miscarriage, preterm labor and some health problems in the newborn. Until more studies have examined garlic's effect on pregnancy, avoid taking supplements made from it.

People with Bleeding Disorders

Garlic can increase the risk of excessive bleeding and bruising in people with bleeding disorders such as von Willebrand disease and hemophilia. If you have a bleeding disorder, it is generally acceptable to eat garlic in food, but most practitioners regard bleeding disorders as a garlic contraindication when it comes to concentrated or supplements in medicinal doses.

People Scheduled to have Surgery

Garlic can increase the risk of bleeding before or after surgery, because it can impair blood clotting. You should stop taking garlic at least two weeks before any surgical procedure, including minor procedures such as dental extractions. If you need emergency surgery, be sure to tell your practitioner that you take garlic; they can make extra precautions to prevent bleeding and other complications.

People taking Isoniazid

If you take the prescription drug isoniazid, sold under the brand names INH and Nydrazid, you should not use garlic. Garlic can decrease the effectiveness of isoniazid, leading to negative and potentially dangerous consequences.

People taking NNRTIs

If you are taking a medication in the class of drugs known as Non-Nucleoside Reverse Transcriptase Inhibitors, or NNRTIs, you should not take garlic. Garlic can increase how fast the body breaks down these drugs, decreasing their effectiveness.

People taking Saquinavir

Do not use garlic if you take the prescription drug saquinavir (sold as Fortovase or Invirase). Garlic increases the rate at which the body metabolizes saquinavir, so it will decrease its effects.