Caffeine: moderate per cup. Limit if you're sensitive, pregnant or breastfeeding (common advice during pregnancy is to limit total daily caffeine to no more than 200 mg). Avoid late in the day if it affects sleep or palpitations.
Stomach sensitivity: Raw sheng pu-erh is more astringent and may worsen reflux, gastritis or ulcers on an empty stomach. If you're sensitive, brew lighter & take with food/drink.
Iron absorption: Tea tannins block non-haem iron uptake. Don't drink with iron-rich food or iron supplements. Leave an additional 2-3 hours between sessions.
Kidney stones: tea contains oxalates. Those with a history of calcium oxalate stones should take modest doses and be well hydrated.
Medication timing: Tee reduces absorption of some medicines & minerals like levothyroxine, iron, calcium & magnesium. Medicines should be taken with water and separated from tea at least 2 hours before taking them.
Fermented product considerations: Poor storage may result in microbial contamination or moldy/moulded tea. Buy from reputable suppliers - avoid damp or mouldy product - rinse leaves briefly - and brew in near-boiling water.
Biogenic amines: As fermented product, trace amounts of histamine/other amines are possible. If you have histamine intolerance or take MAO-inhibitor medicines, use with caution and monitor how you feel.
Dental staining: Teeth stained by strong tea - often. Good oral hygiene helps.