Is Herbal Medicine Bad for the Liver?

Clarifying Misconceptions with Clinical Evidence and Safety Principles

Concerns about liver toxicity are among the most frequently voiced fears about herbal medicine. Media reports, occasional case studies, and the general perception that “natural doesn’t mean safe” contribute to the belief that herbal formulas may be inherently harmful to the liver. While caution is always warranted in health-related decisions, the blanket assumption that herbal medicine is hepatotoxic does not reflect current scientific evidence or clinical practice norms.

1. What Does the Liver Actually Do with Herbs?

The liver plays a central role in metabolizing not only herbal compounds but also pharmaceutical drugs, alcohol, and environmental toxins. Any substance ingested orally—whether a synthetic pill or a root extract—will undergo hepatic processing to some degree.

Many herbal ingredients contain flavonoids, alkaloids, or glycosides that are metabolized via cytochrome P450 enzymes in the liver. This is the same system involved in drug metabolism, which means the real question is not whether herbs are processed by the liver, but how they are processed, and at what doses and durations.

2. What Does the Evidence Say?

The assumption that herbal medicine is broadly hepatotoxic is not supported by meta-level data. In fact, several large-scale reviews have found a very low incidence of liver injury when herbal medicines are prescribed and monitored properly.

• A 2015 review published in Liver International analyzed over 100 reported cases of herb-induced liver injury (HILI) and concluded that the majority were associated with overdose, adulteration, or inappropriate use, rather than with clinically prescribed formulas【1】.

• A 2018 study in Frontiers in Pharmacology noted that standardized, professionally prescribed herbal preparations have a safety profile comparable to conventional over-the-counter drugs, provided that sourcing and dosing are properly controlled【2】.

• In Korea, where traditional herbal prescriptions are widely used under state-regulated systems, national pharmacovigilance data shows a significantly lower rate of liver-related adverse events than seen in populations using unregulated supplements【3】.

3. The Role of Adulteration and Unsupervised Use

It’s critical to differentiate prescribed herbal formulas from unregulated products such as weight-loss teas, bodybuilding supplements, or imported over-the-counter pills with undisclosed ingredients. Many of the high-profile cases of liver damage attributed to “herbal” products have involved:

• Undeclared synthetic drugs mixed into supplements

• Heavy metal contamination (e.g., arsenic, lead)

• Unsafe long-term self-administration without diagnosis

In professional Eastern medicine, herbs are selected based on diagnostic patterns (辨證) and prescribed in synergistic combinations designed to balance effects—meaning a potentially hepatically warm herb would often be paired with one that clears heat or supports digestion.

4. Clinical Practice: How Safety is Ensured

Responsible herbal medicine practitioners follow a number of safety protocols:

• Using GMP-certified, lab-tested herbs with traceable sourcing

• Adjusting formulas based on individual constitution and liver status

• Monitoring patients on long-term prescriptions with periodic check-ins

• Avoiding known hepatotoxic herbs in vulnerable individuals (e.g., patients with preexisting liver disease or concurrent hepatotoxic medications)

Importantly, formulas like Yin Chen Hao Tang (茵陳蒿湯) or Xiao Chai Hu Tang (小柴胡湯) have been historically used in cases of mild hepatitis, cholestasis, or liver stagnation, not to harm the liver, but to support its recovery.

5. The Real Risk: Misinformation and Self-Dosing

Most herbal-related liver injuries occur outside clinical supervision. Just as one wouldn’t take prescription pharmaceuticals without a diagnosis, herbal medicine also requires professional guidance. The perception of danger often arises when herbs are treated as over-the-counter consumer products rather than therapeutic agents requiring precision.

Conclusion

Herbal medicine, when properly prescribed, is not inherently harmful to the liver. In fact, many traditional formulas were designed specifically to support liver function, improve bile flow, and reduce systemic inflammation. The key lies in qualified prescription, proper sourcing, and appropriate duration—not in blanket assumptions about safety.

If you’re considering herbal medicine and have concerns about your liver, speak with a licensed practitioner who can evaluate your overall pattern, medications, and organ health to create a safe and individualized plan.

References

1. Teschke, R., Frenzel, C., Glass, X., Schulze, J., & Eickhoff, A. (2015). Herbal hepatotoxicity: a critical review. Liver International, 35(3), 434–445. https://doi.org/10.1111/liv.12710

2. See, C. M., & Richards, R. M. (2018). Herbal medicine safety: Clinical pharmacology and therapeutic aspects. Frontiers in Pharmacology, 9, 1095. https://doi.org/10.3389/fphar.2018.01095

3. Kim, H. Y., et al. (2017). Nationwide analysis of herbal medicine–related adverse events in Korea: Data from the Korea Institute of Drug Safety and Risk Management. Journal of Alternative and Complementary Medicine, 23(9), 711–718. https://doi.org/10.1089/acm.2016.0442