Because of the potential for side effects and interactions with medications, you should only take dietary supplements under the supervision of a knowledgeable provider.

Yarrow may interact with the following medications:

Blood-thinning medications

High doses of yarrow may slow down blood clotting. If taken with medications that thin the blood, such as aspirin, clopidogrel (Plavix), and warfarin (Coumadin), it may raise the risk of bleeding.

Lithium

Yarrow may increase the amount of lithium in the body, leading to dangerous levels.

Medications to reduce stomach acid

Because yarrow may increase the production of stomach acid, it can interfere with both over-the-counter and prescription drugs, including:

• Cimetidine (Tagamet)
• Famotidine (Pepcid)
• Ranitidine (Zantac)
• Esomeprazole (Nexium)
• Omeprazole (Prilosec)
• Lansoprazole (Prevacid)

Medications for high blood pressure

Yarrow may lower blood pressure slightly and could strengthen the effects of prescription drugs taken to lower blood pressure.

Drugs that cause sleepiness

Because yarrow is a mild sedative, it can increase the effects of other drugs you take for anxiety or sleepiness. These include:

• Anticonvulsants, such as phenytoin (Dilantin)
• Barbiturates
• Benzodiazepines, such as alprazolam (Xanax) and diazepam (Valium)
• Drugs for insomnia, such as zolpidem (Ambien), zaleplon (Sonata), eszopiclone (Lunesta), ramelteon (Rozerem)