Lithium is a mood-stabilizing medication used primarily to treat bipolar disorder. It remains one of the oldest and most effective psychiatric drugs in use, with a track record stretching back more than 70 years. Unlike most psychiatric medications, lithium isn’t a complex synthetic compound. It’s a simple element, the lightest metal on the periodic table, delivered as a salt (usually lithium carbonate) that fundamentally changes how the brain regulates mood.
What Lithium Treats
Lithium’s primary role is managing bipolar disorder, a condition marked by swings between manic highs and depressive lows. International clinical guidelines from 2025 list lithium as a first-line treatment for acute mania, long-term maintenance, and even acute bipolar depression, though its evidence for depression specifically is more mixed. For maintenance therapy, it sits alongside a handful of other medications as one of the most broadly supported options for preventing future manic and depressive episodes.
What truly sets lithium apart from other mood stabilizers is its effect on suicide risk. A meta-analysis covering more than 85,000 person-years of data found that suicides and suicide attempts were approximately 80% lower among people taking lithium compared to those not on it. No other psychiatric medication has demonstrated this kind of consistent protection against self-harm, which is one reason clinicians continue to favor it despite its drawbacks.
How It Works in the Brain
Lithium’s exact mechanism isn’t fully mapped, but the leading explanation centers on an enzyme called GSK-3 that plays a broad role in cell signaling, mood regulation, and brain cell survival. Lithium blocks this enzyme in two ways. First, it directly competes with magnesium, which the enzyme needs to function. Second, it triggers a chain reaction through other signaling proteins that further dials down the enzyme’s activity. The net effect is a kind of chemical stabilization, dampening the overactive signaling pathways associated with mania while supporting pathways that protect neurons.
This isn’t a simple “more serotonin” or “less dopamine” story. Lithium acts on multiple systems simultaneously, which likely explains both its broad effectiveness and why it took decades to piece together what it actually does at the molecular level.
A Brief History
Lithium’s psychiatric use was discovered almost by accident. In 1949, an Australian psychiatrist named John Cade was working at a veterans’ hospital near Melbourne, investigating whether uric acid might play a role in mania. He used lithium salts to dissolve uric acid for his experiments and noticed that the lithium itself had a calming effect on lab animals. He then gave lithium carbonate and lithium citrate to 10 manic patients. Some responded remarkably well, returning to essentially normal functioning and leaving the hospital after years of illness. That study launched lithium into modern psychiatry, though it took until 1970 for the FDA to approve it in the United States.
Blood Levels and Monitoring
Lithium has one of the narrowest therapeutic windows of any commonly prescribed drug. The difference between an effective dose and a toxic one is small, which is why regular blood tests are non-negotiable for anyone taking it. For long-term maintenance in adults with bipolar disorder, the recommended target is a serum concentration of 0.60 to 0.80 mmol/L. If someone responds well but has bothersome side effects, that target can be lowered to 0.40 to 0.60 mmol/L. If the response isn’t strong enough, it can be raised to 0.80 to 1.00 mmol/L. Going above 1.00 mmol/L doesn’t appear to offer additional benefit for maintenance, though higher levels are sometimes used briefly for acute mania.
Before starting lithium, a standard workup includes blood counts, kidney function tests (blood urea nitrogen and creatinine), thyroid function tests, calcium levels, a urinalysis, and a pregnancy test for women of childbearing age. These baselines matter because lithium can affect kidney and thyroid function over time, and clinicians need a reference point to track changes.
Side Effects and Risks
Common early side effects include increased thirst, frequent urination, mild tremor in the hands, weight gain, and digestive issues like nausea. Many of these improve as the body adjusts, and keeping blood levels in the lower end of the therapeutic range helps. Cognitive complaints, often described as feeling mentally “dulled” or slower, are another reason some people struggle with long-term use.
The two organs most affected over years of lithium use are the kidneys and thyroid. Lithium can impair the kidneys’ ability to concentrate urine, leading to a condition where you produce large volumes of dilute urine and feel constantly thirsty. It can also suppress thyroid function, sometimes enough to require thyroid hormone replacement. These risks are manageable with regular monitoring, but they’re the main reason lithium demands more medical oversight than most psychiatric medications.
Lithium toxicity is the most serious acute risk. Early signs include severe nausea, vomiting, diarrhea, coarse tremor, slurred speech, and confusion. Toxicity can progress to seizures and organ damage if levels climb high enough. Dehydration, illness, and certain medications can push lithium levels dangerously high even when your prescribed dose hasn’t changed.
Medications That Interact With Lithium
Several widely used drug classes can raise lithium levels in the blood, increasing the risk of toxicity. Common anti-inflammatory painkillers like ibuprofen and naproxen reduce the kidneys’ ability to clear lithium by decreasing blood flow to the filtering units. People on lithium are generally advised to avoid these entirely and use acetaminophen instead. Blood pressure medications, specifically ACE inhibitors and a related class called angiotensin receptor blockers, also raise lithium concentrations. Thiazide diuretics, a common type of water pill prescribed for blood pressure, increase sodium reabsorption in the kidneys, which in turn causes the body to hold onto more lithium.
If any of these medications are medically necessary, the combination can sometimes be managed with closer blood monitoring and dose adjustments, but it requires careful coordination.
Lithium in Drinking Water
One of the more intriguing areas of lithium research involves trace amounts of the element that occur naturally in drinking water. Concentrations vary dramatically by geography, and a growing body of evidence suggests that even tiny amounts may have population-level effects on brain health. A systematic review of five studies found that communities with higher trace lithium in their water supply had lower rates of dementia incidence and dementia-related mortality. The protective association appeared at concentrations as low as 0.002 mg/L, far below anything resembling a therapeutic dose. Below that threshold, the effect disappeared.
Some researchers have noted that women may be more sensitive to these trace-level effects. The findings are still preliminary, and the studies haven’t fully controlled for other factors that might explain the pattern. But the consistency of the association across multiple countries and study designs has kept the topic alive in neuroscience circles, raising questions about whether lithium plays a broader role in brain health than its psychiatric use alone would suggest.