Pau d'Arco Side Effects and Safety: What You Need to Know

Pau d'Arco is often described as the "Divine Tree" of the Amazon, used for centuries by indigenous tribes. But "natural" doesn't mean "without rules." If you're considering it, it's worth understanding the safety profile as clearly as the benefits.

The Main Culprit: Lapachol

The primary active compound is a naphthoquinone called lapachol.

Traditional herbalists point out that whole inner bark (the phloem) contains other compounds that may moderate lapachol's intensity — which is why sourcing whole, authentic inner bark (rather than isolated extracts or fillers) matters; see our inner bark sourcing guide.

Common Side Effects

For most people, a standard decoction is well-tolerated. At higher doses or on an empty stomach, some people report:

• Nausea and vomiting — the most common reaction, especially with concentrated extracts.
• Dizziness or lightheadedness — occasionally reported at higher doses.
• Discolored urine — a slight color change (often deeper yellow or orange) generally considered a harmless byproduct of quinone metabolism.
• Diarrhea — at very high doses, the bark can act as a mild laxative.

If you experience these, the standard guidance is to reduce your dose or pause use.

Serious Interactions: The Blood-Thinning Factor

Because of this, avoid combining Pau d'Arco with:

• Prescription blood thinners — Warfarin (Coumadin), Heparin, Clopidogrel (Plavix).
• NSAIDs — Ibuprofen (Advil/Motrin), Naproxen (Aleve), high-dose Aspirin.
• Other blood-thinning herbs — garlic, ginger, turmeric, or ginkgo biloba, which can have an additive effect.

Surgery: stop all forms of Pau d'Arco at least two weeks before any scheduled surgery.

What a Small Human Safety Trial Found

Pending medical review. This section was added on September 26, 2026 and has not yet been reviewed by our medical reviewer.

Who Should Avoid Pau d'Arco Entirely

• Pregnant women — animal studies have suggested lapachol may have abortifacient properties. Human safety data is sparse, but the risk is treated as high enough to contraindicate use during pregnancy.
• Nursing mothers — insufficient data on whether active compounds pass through breast milk.
• Infants and children — no established safe pediatric dosage.
• People with bleeding disorders — such as hemophilia.

Dosage and Preparation

Traditional and research sources both point to the decoction method — simmering the bark rather than steeping it — as standard, and our own method cooks it for about 25 minutes. Avoid high-dose, isolated lapachol capsules; isolating one compound loses the whole-plant synergy, which is where toxicity concerns have historically shown up. See our brewing guide and Why the Inner Bark Is Important for more on why the whole inner bark, not an isolate, is the traditional and better-tolerated form.

Starting Out and Adjusting

Pending medical review. This section was added on September 26, 2026 and has not yet been reviewed by our medical reviewer.

A gradual start makes it easier to notice how your body responds. Many people begin with one cup a day and add a half cup each week until they find the amount that suits them. Avoid starting several new supplements at the same time, so you can tell what is causing any reaction. Some people report mild digestive changes or tiredness in the first few days. That is anecdotal: there is no clinical evidence defining it as a specific reaction to pau d'arco. Treat it like any other side effect. Cut back, and check with a healthcare provider if it is significant or does not settle.

A Note on Quality and Sourcing

Some reported "side effects" trace back to contaminants or low-grade fillers rather than Pau d'Arco itself — outer bark contains more tannins and fewer active compounds, which can irritate the stomach. Look for Handroanthus impetiginosus (formerly Tabebuia avellanedae) inner bark specifically; we source ours through Taheebo Wellness Tea.

Summary of Safety Precautions

• Start low and go slow — a small cup first, to see how your body reacts.
• Watch for unusual bruising, bleeding gums, or persistent nausea.
• Consider cycling use (e.g., five days on, two days off).
• Check your medications with your doctor if you're on any long-term prescriptions.

References

1. 1.Molecules (2020): "Tabebuia impetiginosa: A Comprehensive Review on Traditional Uses, Phytochemistry, and Immunopharmacological Properties."
2. 2.Journal of Ethnopharmacology (2006): "Inhibitory effects of Tabebuia impetiginosa inner bark extract on platelet aggregation and vascular smooth muscle cell proliferation."
3. 3.Advanced Integrative Medicine (2022): "Safety and tolerability of Pau d'Arco (Tabebuia avellanedae) for primary dysmenorrhea."
4. 4.Phytotherapy Research (2013): "Antiulcer effect of bark extract of Tabebuia avellanedae: activation of cell proliferation in gastric mucosa."
5. 5.Genetics and Molecular Biology (2012): "Genotoxic effects of Tabebuia impetiginosa (Mart. Ex DC.) Standl. extract in Wistar rats."
6. 6.Block, J.B., et al. (1974). "Early clinical studies with lapachol (NSC-11905)." Cancer Chemotherapy Reports, Part 2. (NCI Phase I data)