Phase 1 · Understand the Body — Why the disease behaves the way it does.
The One-Line Truth
The whole disease in one chain
Everything on this page exists to explain this line.
Lithium's safe window is narrow (0.6–1.2 mEq/L), and anything that drops your body's water or raises sodium—dehydration, diuretics, NSAIDs, kidney trouble—can push lithium into the danger zone fast.
The Clogged Drain and the Backed-Up Sink
Imagine lithium as tiny pebbles flowing down a kitchen sink drain (your kidneys). Normally, the drain grate (the proximal tubule's sodium transporters) lets most pebbles wash straight out to the sewer (urine), keeping just a few in the sink bowl (blood). But when you turn off the faucet (dehydration) or block the main drain pipe (take an NSAID), water backs up in the sink. The drain tries to save water by pulling it back up, but the pebbles ride that reverse current too—so pebbles pile up in the bowl instead of leaving. Meanwhile, your sink's strainer basket (the collecting duct) is supposed to catch big debris and send water down, but lithium gums up the basket's hinges (aquaporin-2 channels), so it jams open and water leaks everywhere (nephrogenic DI). While the pebbles sit in your bowl, they scratch the porcelain (neurons and heart cells), causing cracks that spread fast once there are enough of them.
American College of Medical Toxicology (ACMT) lithium position statement 2018 · UpToDate clinical guideline on lithium toxicity · Kidney Disease: Improving Global Outcomes (KDIGO) lithium guidance · American Academy of Clinical Toxicology practice guidelines · reviewed 2026-07-07