Note: this section refers to OTC nutrient doses (≤20 mg elemental Li/day). Pharmaceutical lithium carbonate side effects are categorically different and dose-dependent.

• Common (>10% users) at OTC dose: None reliably. Most users report nothing.
• Less common (1-10%) at OTC dose:
  • Mild lethargy / flat affect. A subset of users report feeling "muted" or slightly tired in the first 1-2 weeks. Usually resolves with adaptation or by reducing dose. If persistent, discontinue.
  • Mild GI (nausea, loose stool) — uncommon at 5-10 mg but reported at 20 mg+, especially on empty stomach. Resolves with food or dose reduction.
  • Mild fine tremor — rare at OTC dose, more common at 15-20 mg. If present, discontinue or reduce.
• Rare-serious (<1% but worth knowing) at OTC dose:
  • Thyroid: No documented hypothyroidism at strict OTC doses (≤10 mg elemental Li) in healthy adults. Theoretical risk exists because thyroid is the most sensitive organ to lithium effects (affects iodide uptake + thyroid hormone release). Annual TSH check is reasonable for chronic users above 10 mg/day. Pre-existing thyroid disease (Hashimoto's, subclinical hypo) lowers the threshold for monitoring.
  • Renal: No documented nephrogenic diabetes insipidus or interstitial nephritis at OTC doses. The pharma-dose cumulative-exposure risk does not extrapolate cleanly to 20× lower dose.
  • Calcium / parathyroid: Pharma-dose lithium can elevate serum calcium and parathyroid hormone. Not documented at OTC dose.
  • Cardiac (long QT, sinus node): Very rare even at pharma dose. Not a concern at OTC.
• Toxicity threshold: Effectively absent. To reach toxic serum lithium (~1.5 mEq/L) from lithium orotate would require swallowing several full bottles in a single sitting. Not a realistic risk profile.
• Specific watch periods: First 2-3 weeks for subjective lethargy / flat affect (most common reason to discontinue). At month 3 and annually if continuing, optional TSH + creatinine + serum Li for peace of mind, especially at 10+ mg/day.

Pregnancy: Lithium at any dose has historical concern for cardiac (Ebstein's anomaly) malformations at pharma dose; the OTC-dose risk is probably negligible but not formally studied. Avoid in pregnancy as a default. Not relevant for users in this archetype.

Pre-existing renal disease, thyroid disease, dehydration-prone: Lower the threshold for monitoring. At the user's age and health, none of these apply.