Lithium carbonate is a mood-stabilizing medication used primarily to treat bipolar disorder. It contains lithium, one of the simplest elements on the periodic table, formulated as a salt that the body can absorb. Despite being one of the oldest psychiatric medications still in wide use, it remains a first-line treatment for both acute manic episodes and long-term mood stabilization, largely because nothing else matches its track record for preventing the extreme highs and lows of bipolar disorder.
What Lithium Carbonate Treats
Lithium carbonate is approved to treat manic episodes in bipolar disorder and to prevent their recurrence. During a manic episode, a person may feel euphoric, sleep very little, act impulsively, or experience racing thoughts that spiral out of control. Lithium brings these episodes down and, when taken continuously, reduces the likelihood of future episodes on both ends of the spectrum: mania and depression.
It is sometimes prescribed off-label for treatment-resistant depression, certain headache disorders, and aggressive behavior, though bipolar disorder is by far its primary use.
How It Works in the Brain
Lithium affects the brain through several overlapping pathways, which is part of why it took decades to understand and why it works so broadly.
One of its key actions is blocking an enzyme called GSK-3 beta. This enzyme plays a role in cell signaling, inflammation, and how brain cells grow and survive. By dialing it down, lithium influences a cascade of protective processes inside neurons. It also tunes neurotransmitter activity: it reduces dopamine signaling (which likely explains its ability to calm mania) and enhances serotonin transmission (which may contribute to its antidepressant effects).
Beyond mood regulation, lithium appears to be genuinely neuroprotective. It boosts production of a protein called BDNF, which supports the growth and survival of brain cells. It strengthens mitochondria, the energy-producing structures inside cells, making neurons more resistant to oxidative stress. There’s even evidence that lithium normalizes telomere length in people with bipolar disorder. Telomeres are the protective caps on chromosomes that shorten with age and stress, so this finding suggests lithium may counteract some of the accelerated cellular aging seen in the condition.
The Narrow Therapeutic Window
Lithium is unusual among psychiatric medications because the difference between a helpful dose and a harmful one is small. This is why people taking it need regular blood tests to check their serum lithium level.
For acute manic episodes, the target blood level is 0.8 to 1.2 mEq/L. For long-term maintenance, the target drops slightly to 0.8 to 1.0 mEq/L. Treatment typically starts at 600 mg taken two to three times daily, then gets adjusted based on blood levels. Maintenance doses range from 300 to 600 mg, two to three times daily.
Because the margin is tight, anything that changes how your kidneys handle sodium can shift lithium levels. Dehydration, heavy sweating, fever, vomiting, or diarrhea can all push levels higher. So can several common medications.
Medications That Raise Lithium Levels
Three classes of drugs are particularly important to watch. Diuretics (water pills), ACE inhibitors, and ARBs, all commonly prescribed for blood pressure, cause the body to lose sodium. When sodium drops, the kidneys hold on to more lithium, and blood levels rise. NSAIDs like ibuprofen and naproxen do the same thing. In one study, the common anti-inflammatory celecoxib raised steady-state lithium levels by about 17%. Even over-the-counter pain relievers in this category can be enough to tip someone into toxicity, so anyone on lithium should check with their prescriber before taking common painkillers.
Common Side Effects
Lithium’s side effects are well documented, and most people on it experience at least one.
- Increased thirst and urination: This is the most common long-term side effect, reported in up to 70% of patients on chronic therapy. Lithium affects the kidneys’ ability to concentrate urine, so you produce more of it and feel thirstier as a result.
- Hand tremor: A fine tremor, especially in the hands, affects roughly one in four people taking lithium. It tends to be mild but can be noticeable when writing or holding a cup.
- Weight gain: About 73 to 77% of people on lithium gain weight. In one study, the average gain was about 6.3 kg (around 14 pounds), and 20% of patients gained 10 kg (22 pounds) or more.
Other common effects include nausea, mild cognitive dulling (sometimes described as feeling mentally “slower”), and acne or skin changes. Many of these are dose-dependent, meaning they improve if the blood level can be brought to the lower end of the therapeutic range.
Long-Term Effects on the Kidneys and Thyroid
The two organs that need the most watching over years of lithium use are the kidneys and the thyroid.
Kidney Function
Long-term lithium use gradually reduces the kidneys’ concentrating ability by about 15% and can lower the filtration rate by up to 5 mL per minute per year. Most people tolerate this without serious consequences, but the risk of developing stage 3 chronic kidney disease is roughly double that of the general population. In a study of 180 long-term lithium patients in Israel, 13 had progressed to stage 3 kidney disease and 2 required dialysis. These numbers are relatively small, but they’re the reason regular kidney monitoring is non-negotiable for anyone on this medication.
Thyroid Function
Lithium interferes with thyroid hormone production. A review of 77 studies found a six-fold increased risk of clinical hypothyroidism in people taking lithium for an average of about six years, and a four-fold increased risk of elevated TSH (the hormone that signals an underactive thyroid) after just a year and a half. In one long-term cohort, 22% of female patients showed features of hypothyroidism. The good news is that this is easily managed with thyroid hormone replacement, and it rarely requires stopping lithium.
Ongoing Monitoring
People on lithium need a consistent schedule of blood work. Before starting treatment, baseline tests typically include kidney function (creatinine and eGFR), thyroid function (TSH), and a full blood count. Once treatment is underway, lithium blood levels are checked frequently at first, then every few months once stable. Kidney and thyroid labs are monitored at least once or twice a year, often more frequently in people with declining function.
You should also be aware of symptoms that warrant prompt attention: persistent vomiting or diarrhea (which can spike lithium levels), unusual fatigue or cold sensitivity (signs of hypothyroidism), and dramatically increased urination or thirst (signs of kidney strain). Persistent headache with visual changes, though rare, can indicate increased pressure inside the skull.
Signs of Lithium Toxicity
Toxicity happens when blood levels climb above 1.5 mEq/L. It’s divided into three stages:
- Mild (1.5 to 2.5 mEq/L): Nausea, vomiting, hand tremor worse than usual, fatigue, and sluggishness.
- Moderate (2.5 to 3.5 mEq/L): Confusion, agitation, delirium, rapid heart rate, and muscle stiffness.
- Severe (above 3.5 mEq/L): Seizures, coma, dangerously low blood pressure, and high body temperature. This is a medical emergency.
Toxicity can develop gradually from a slow rise in levels (often triggered by dehydration or a new medication) or acutely from an overdose. The early symptoms, especially nausea and worsening tremor, are the warning signs to act on before things progress.