Common at LDN doses (>10% users):

• Vivid dreams (very common, week 1-3, often resolves)
• Insomnia or sleep disruption (week 1-2, often resolves)
• Mild headache (week 1-2)
• Mild GI upset (transient)

Less common at LDN (1-10%):

• Persistent insomnia (require AM dosing or dose reduction)
• Mild fatigue (paradoxical; usually transient)
• Mild dysphoria / anhedonia (suggests over-blockade of tonic endorphin tone — usually responds to dose reduction)
• Mild irritability week 1
• Nausea

Common at 50 mg standard dose (>10%):

• Nausea, headache, fatigue, sleep changes — substantially more than LDN
• Hepatotoxicity-relevant transaminase elevations (see below)

Rare-serious (<1% but worth knowing):

• Precipitated opioid withdrawal: if naltrexone is given to someone using opioids (prescription or recreational), even at LDN doses, withdrawal is precipitated within minutes — severe nausea, vomiting, diarrhea, agitation, autonomic storm. A user in this archetype does not use opioids so this is not a personal risk, but becomes critical if they are given opioids in an emergency context while on LDN (less acute than the reverse direction, but still relevant).
• Hepatotoxicity: at high doses (>200 mg/day in early studies) — black-box warning on the package insert. At standard 50 mg this is rare but transaminase elevations can occur. At LDN doses (1.5-4.5 mg) hepatotoxicity is essentially not documented — the dose is far below the threshold. Still, baseline + 3-month LFTs are conservative and easy.
• Suicidal ideation (rare, reported with standard dose, mainly in OUD patients with comorbid depression — not LDN-associated in the literature)
• Allergic reaction (rare; some users report sensitivity to compounding fillers rather than to naltrexone itself — switching pharmacy can help)

Specific watch periods:

• Week 1-3 LDN: vivid dreams + sleep disruption is the typical dropout window. Most users push through; some require dose reduction.
• Week 4-8 LDN: efficacy assessment window. If no benefit at 4.5 mg by week 8-12, reassess — LDN is not effective for everyone.
• First 90 days standard dose: LFT monitoring conservative; not strictly required but recommended.