Lithium for Bipolar Disorder: What You Need to Know

Lithium is the oldest and most studied mood stabilizer in psychiatry. It has been in continuous clinical use since 1949, when Australian psychiatrist John Cade first documented its antimanic effects. More than seven decades later, it remains one of the most effective treatments for bipolar disorder — and one of the most misunderstood.

If your doctor has recommended lithium, or if you are already taking it and want a clearer picture of what the drug does and demands, this guide covers the essentials.

What Lithium Does

Lithium is a naturally occurring element — the lightest solid metal on the periodic table. Its exact mechanism of action in bipolar disorder is still not fully understood, despite decades of research. What is known is that it affects multiple neurotransmitter systems and intracellular signaling pathways. It appears to stabilize nerve cell membranes, modulate glutamate signaling, and influence circadian rhythms.

In clinical terms, lithium does three things well:

• Treats acute mania. Lithium can bring a manic episode under control, though it works more slowly than antipsychotics and is therefore sometimes used alongside them in the early stages of treatment.
• Prevents future episodes. This is its primary role. Long-term lithium maintenance significantly reduces the frequency and severity of both manic and depressive episodes.
• Reduces suicide risk. Lithium is the only psychiatric medication with robust evidence of reducing suicidal behavior. A 2013 meta-analysis in the BMJ found that lithium reduced the risk of suicide and self-harm by more than 60% compared to placebo.

Blood Levels and Monitoring

Lithium has what pharmacologists call a narrow therapeutic index. The blood level that provides benefit is not far from the level that causes toxicity. This is the central fact of lithium treatment: it works, but it requires respect.

The typical therapeutic range is 0.6 to 1.0 milliequivalents per liter (mEq/L) for maintenance, and sometimes up to 1.2 mEq/L during acute manic episodes. Levels above 1.5 mEq/L are generally considered toxic, and levels above 2.0 mEq/L can be life-threatening.

When you first start lithium, your doctor will check blood levels frequently — often weekly — until a stable dose is established. After that, monitoring typically moves to every two to three months. Blood should be drawn approximately 12 hours after your last dose, usually first thing in the morning before taking the day's first dose.

What Else Gets Monitored

Beyond lithium levels, your doctor should be tracking several other things:

• Kidney function (creatinine and eGFR). Lithium is processed entirely by the kidneys. Long-term use can gradually reduce kidney function in some patients. This is usually mild and slow, but it needs to be watched. A 2015 review in The Lancet Psychiatry estimated that about 1 in 4 long-term lithium users develop some degree of reduced kidney function, though progression to serious kidney disease is uncommon.
• Thyroid function (TSH, free T4). Lithium can cause hypothyroidism — an underactive thyroid. This occurs in roughly 10-20% of patients and is more common in women. It is treatable with thyroid hormone replacement and does not necessarily mean lithium must be stopped.
• Calcium and parathyroid levels. Lithium can cause elevated calcium and hyperparathyroidism in some patients, usually after years of use.

A typical monitoring schedule after stabilization includes blood levels every 2-3 months, kidney and thyroid function every 6 months, and calcium annually.

Common Side Effects

Not everyone experiences side effects, but they are common enough that you should know what to expect:

• Fine tremor. A slight shaking of the hands, particularly noticeable when holding small objects or writing. This is the most common side effect and is usually manageable. If it becomes bothersome, a low dose of propranolol can help.
• Increased thirst and urination. Lithium affects the kidneys' ability to concentrate urine. You will likely need to drink more water than usual. This is expected, not a sign of toxicity.
• Weight gain. Varies widely between individuals but averages around 4-6 kg (about 10-13 lbs) over the first two years.
• Gastrointestinal effects. Nausea, loose stools, and stomach discomfort, particularly early in treatment. Taking lithium with food usually helps.
• Cognitive effects. Some people report feeling mentally "dulled" or slower. This is dose-dependent and should be discussed with your doctor if it affects your quality of life.
• Acne and skin changes. Less commonly discussed but not rare.

Things That Affect Lithium Levels

Because lithium is excreted by the kidneys, anything that changes kidney function or hydration status can shift your lithium level. This is critical to understand:

• Dehydration concentrates lithium in the blood. Vomiting, diarrhea, heavy sweating (exercise in heat), and fever all raise your risk. When you are dehydrated or ill, your lithium level climbs.
• NSAIDs (ibuprofen, naproxen, celecoxib) reduce kidney excretion of lithium and can push levels into the toxic range. Acetaminophen (Tylenol) is generally safe.
• ACE inhibitors and ARBs (common blood pressure medications) also increase lithium levels.
• Diuretics, particularly thiazides, can significantly increase lithium levels. If a diuretic is necessary, your doctor should adjust your lithium dose and monitor levels closely.
• Caffeine increases lithium excretion. Sudden large changes in caffeine intake — starting or stopping heavy coffee drinking — can shift your levels.
• Sodium intake. Low-sodium diets increase lithium retention. Keep your salt intake relatively consistent from day to day.

Lithium and Pregnancy

Lithium crosses the placenta and was long thought to carry a high risk of a specific heart defect called Ebstein's anomaly. More recent and larger studies have revised the risk estimate downward. A 2017 cohort study in the New England Journal of Medicine found that the absolute risk of cardiac malformations with first-trimester lithium exposure was about 2%, compared to roughly 1% in the general population. The risk is real but smaller than previously believed.

The decision about lithium during pregnancy is complicated and must be made individually, weighing the risk of medication exposure against the risk of untreated bipolar disorder during pregnancy and postpartum. This is a conversation for you, your psychiatrist, and your obstetrician.

Stopping Lithium

Do not stop lithium abruptly. Sudden discontinuation significantly increases the risk of a relapse, particularly a manic episode, and the risk is higher than it would be if you had never started lithium at all. This is one of the better-established findings in the lithium literature.

If you and your doctor decide to taper off lithium, the process should be gradual, typically over at least two to four weeks and ideally longer. Even with a slow taper, the risk of relapse increases, so close monitoring during and after discontinuation is essential.

Is Lithium Right for You?

Lithium works best for people with classic bipolar presentations: clear episodes of euphoric mania and depression with relatively normal functioning in between. It is particularly worth considering if you have a family member who responded well to lithium, as response tends to run in families. It is also the strongest choice if suicide risk reduction is a priority.

It may be less ideal for people who have difficulty with regular blood monitoring, those with significant kidney disease, or those whose primary problem is rapid cycling, for which the evidence is less strong.

Like any psychiatric medication, lithium is not a miracle drug. It is a tool that works well for many people, demands some vigilance in return, and has trade-offs worth understanding clearly. The best outcomes come from informed patients working with attentive clinicians.