Hawthorn is generally safe for most adults. Clinical trials lasting up to two years have found no serious adverse reactions linked to standardized hawthorn extract, and side effects tend to be mild and temporary. That said, there are specific situations where hawthorn carries real risks, particularly if you take heart medications, are pregnant, or have surgery coming up.
Common Side Effects
Most people tolerate hawthorn well. A systematic review of adverse event reports found that the most frequently reported issues were gastrointestinal complaints (upset stomach, nausea, diarrhea), dizziness, headache, and palpitations. These side effects are uncommon and typically mild. Rare cases of skin rash and allergic reactions have been described, but they’re the exception.
In the largest long-term safety trial, over 1,300 people took 900 mg of hawthorn extract daily for two years. The rate of adverse events in the hawthorn group was essentially identical to the placebo group (67% vs. 68%), and no side effects specific to hawthorn were identified. That’s a strong signal for a supplement with this much clinical data behind it.
Doses Used in Studies
Clinical trials have tested hawthorn extract at doses ranging from 240 mg to 1,800 mg per day. Doses of 900 mg daily are the most commonly studied, while one trial used 1,800 mg per day with no reported side effects. These studies used a standardized extract (WS 1442), which is made from hawthorn leaves and flowers and contains consistent levels of active compounds called oligomeric procyanidins and flavonoids. If you’re choosing a supplement, look for a standardized extract rather than a raw berry powder, since that’s what the safety data is actually based on.
The Digoxin Interaction
If you take digoxin, a common heart medication, hawthorn is one supplement you should avoid. Hawthorn contains compounds that are structurally similar to digoxin and appear to bind to the same site on heart cells. This creates two problems: hawthorn can interfere with blood tests that measure your digoxin levels, giving inaccurate readings, and it may amplify the drug’s effects on your heart in unpredictable ways.
Interestingly, a large two-year trial that included patients on multiple heart failure drugs (including digoxin) found no safety signals or evidence of drug interactions. The researchers concluded that co-administration appeared safe in that controlled setting. Still, the theoretical risk and the lab test interference are enough that most guidelines recommend against combining the two.
Other Heart Medications
Hawthorn works partly by strengthening the heart’s contractions, similar in mechanism to digoxin but much milder. It slightly decreases heart rate and increases calcium signaling in heart muscle cells. Because of these effects, there’s a reasonable concern about combining it with beta-blockers, calcium channel blockers, or blood pressure medications, since hawthorn could theoretically amplify their effects and cause your blood pressure or heart rate to drop too low.
In practice, the large clinical trials enrolled patients who were already on standard heart failure medications, and no interaction problems emerged. But those were monitored clinical settings. If you’re on cardiac drugs and want to try hawthorn, your cardiologist needs to know about it.
Pregnancy, Breastfeeding, and Children
Hawthorn is not recommended during pregnancy. Animal studies and human case reports suggest it may stimulate uterine activity, which is enough of a concern to warrant avoidance. For breastfeeding, no data exists on whether hawthorn compounds pass into breast milk or how they might affect an infant. Germany’s Commission E, which evaluates herbal medicines, found no reason to contraindicate hawthorn flowers or leaves during breastfeeding but recommended avoiding the fruit. Most other sources take a more cautious position and suggest skipping it entirely while nursing. There’s also no reliable safety data for children, so it’s not currently recommended for pediatric use.
Stop Before Surgery
Hawthorn has potential anticoagulant effects, meaning it may thin the blood slightly. Because of this, guidelines recommend discontinuing hawthorn supplements at least two weeks before any scheduled surgery. This is the same advice given for garlic supplements and several other herbal products. If you have a procedure coming up, let your surgeon know you’ve been taking hawthorn.
Liver Safety
Hawthorn gets the lowest possible risk score for liver injury from the National Institutes of Health, classified as “unlikely cause of clinically apparent liver injury.” High doses given to dogs in animal studies did cause liver problems, but hawthorn has been used safely in humans for centuries with no pattern of liver toxicity emerging. At standard supplement doses, liver damage is not a realistic concern.
Who Should Be Cautious
The only absolute contraindication is a known allergy to hawthorn (Crataegus) products. Beyond that, the groups who should avoid or be cautious with hawthorn include:
- People taking digoxin, due to pharmacological overlap and lab test interference
- People on blood pressure or heart rate medications, due to potential additive effects
- Pregnant women, due to possible uterine stimulation
- Breastfeeding women and children, due to lack of safety data
- Anyone facing surgery within two weeks, due to possible blood-thinning effects
For a healthy adult not in any of these categories, hawthorn has one of the better safety profiles among herbal supplements. Two-year trials with over 2,600 participants, post-marketing surveillance projects, and decades of traditional use all point in the same direction: it’s well tolerated, side effects are rare and minor, and serious harm is essentially undocumented at standard doses.