Marshmallow root is considered safe for most people, and serious side effects are rare. The U.S. FDA classifies it as a Generally Recognized as Safe (GRAS) food substance. That said, a few side effects and interactions are worth knowing about, especially if you take medications or have an upcoming surgery.
Low Blood Sugar
The most notable side effect of marshmallow root is its potential to lower blood sugar. For most people, this isn’t a problem. But if you take medication for diabetes, the combination can push your blood sugar to dangerously low levels. Marshmallow root contains compounds that reduce blood sugar on their own, and when stacked on top of diabetes medication, the effect can be amplified. Symptoms of low blood sugar include shakiness, dizziness, sweating, confusion, and irritability. If you manage diabetes with medication, talk with your doctor before adding marshmallow root to your routine.
Interference With Medication Absorption
Marshmallow root gets its soothing properties from mucilage, a thick, gel-like substance that coats tissues. That same coating effect can also line your digestive tract in a way that slows or reduces how well your body absorbs oral medications. This applies broadly: any pill or capsule you take by mouth could potentially be affected.
The practical fix is timing. If you take prescription medications, use marshmallow root at least one to two hours before or after your dose. This gives your medication time to be absorbed without the mucilage barrier getting in the way.
Allergic Reactions
Allergic reactions to marshmallow root are reported rarely, but they do happen. If you’re allergic to other plants in the mallow family (which includes hibiscus and hollyhock), you may be more likely to react. Signs of an allergic reaction can include skin irritation, itching, swelling, or difficulty breathing. Marshmallow root is also sometimes applied directly to the skin, where it’s considered possibly safe, though contact reactions are possible in sensitive individuals.
Surgery Concerns
Because marshmallow root can lower blood sugar, it poses a risk during and after surgery, when blood sugar control is critical. The American Society of Anesthesiologists recommends stopping all herbal supplements one to two weeks before a scheduled procedure. Herbal products taken before surgery can cause a range of complications, including blood pressure changes, prolonged sedation, and unpredictable interactions with anesthesia drugs. If you have surgery planned, let your medical team know you’ve been using marshmallow root so they can advise you on when to stop.
Pregnancy and Breastfeeding
There’s very little human data on marshmallow root during pregnancy or breastfeeding. No safety studies have specifically tested it in pregnant or nursing women. The general guidance with herbal supplements in this situation is to err on the side of caution and avoid use unless a healthcare provider says otherwise.
Typical Dosage Ranges
Side effects are more likely when you take large amounts, so knowing standard dosage ranges helps. The German Commission E, a respected authority on herbal medicine, suggests about 6 grams of marshmallow root per day as a baseline. In practice, people often use more when making tea. A typical cup calls for 10 to 15 grams of root steeped in hot water for 15 to 20 minutes, and some people drink three to five cups a day. Cold water preparations use 30 to 45 grams steeped overnight in about three cups of water.
For capsules and tablets, a common range is 5 to 6 grams per day. Tinctures are typically taken as 5 to 15 ml three times daily. Staying within these ranges, most adults tolerate marshmallow root without issues. If you’re new to it, starting at the lower end lets you gauge how your body responds before increasing.