Final answer:
Kava should be reported to a healthcare provider due to its association with severe liver toxicity, especially in patients with already increased liver enzymes.
Step-by-step explanation:
The herbal preparation that should be reported to the provider if a client has increased liver enzymes and is taking herbal supplements is Kava. Kava has been associated with severe liver toxicity, including hepatitis, cirrhosis, and liver failure in some individuals. Despite its use for anxiety relief, due to its potential for causing liver damage, healthcare providers must be notified if a patient with liver issues is taking Kava. The other herbal supplements listed, Ma Huang, Saw Palmetto, and St. John's Wort, have different concerns like drug interactions and cardiovascular risks associated mainly with Ma Huang, but Kava stands out for its direct link to liver health concerns.