When to Stop

• Biliary obstruction worsening — in users with mechanical bile duct obstruction (gallstone in CBD, stricture, tumor), adding bile acids can worsen stasis and pain. Hard contraindication. Rule out obstructive picture (RUQ pain, jaundice, abnormal alkaline phosphatase + GGT pattern) before starting; if any present, see GI/hepatology before supplementing.
• Acute pancreatitis — rare case reports in users with prior pancreatic disease; mechanism speculative (bile-acid reflux). Not a baseline concern in healthy users.
• Allergic / hypersensitivity reactions — case reports exist but exceptionally rare. Stop if rash, swelling, breathing change.
• Fetal exposure (pregnancy) — UDCA has reassuring safety data in second/third trimester pregnancy and is first-line for ICP. First-trimester data is insufficient. TUDCA specifically is even more thinly studied; do not self-prescribe in pregnancy or breastfeeding — defer to hepatology/maternal-fetal medicine.
• First 2 weeks: GI tolerance — loose stools, cramping. Drop dose or stop if intolerable.
• First 4-8 weeks (if running for AAS/modafinil/Tylenol buffer): Recheck ALT/AST at week 8 to verify the buffer is doing what you want.
• No long-term watch period required at standard supplement doses (250-1,000 mg). 1+ year safety from PBC cohorts is reassuring.
• Safer than milk thistle (which has mild ALT-elevation reports in a minority of users and no good RCT signal for liver enzyme normalization in healthy subjects).
• Safer than NAC in terms of GI side effects but NAC has stronger evidence for specific acute toxicities (APAP overdose, contrast nephropathy).
• Roughly equivalent safety to UDCA — TUDCA is the more soluble cousin, marginally better tolerated GI-wise.