Lithium

What lithium is used for

The FDA-approved uses include acute manic episodes in bipolar disorder and maintenance treatment of bipolar I disorder. In clinical practice, lithium is also used for:

• bipolar depression (off-label but with strong evidence)
• augmentation of antidepressants in treatment-resistant unipolar depression (off-label, with evidence)
• reducing suicide risk in bipolar disorder (one of the most consistent findings in psychiatric pharmacology)
• reducing self-harm and impulsive aggression in some contexts

It's used less often for schizoaffective disorder, cluster headaches, and a few other conditions.

For most people who take it, lithium is prescribed for bipolar disorder or for augmentation of an antidepressant for depression.

How it works

The full mechanism isn't fully understood after more than 70 years of use, which is common for older psychiatric medications. What's known: lithium influences second-messenger systems inside neurons (particularly inositol-related and GSK-3 pathways), affects gene expression over weeks, and appears to have some neuroprotective effects. It's not neurotransmitter blockade in the way antidepressants and antipsychotics are. For a visual, see PsychiatryRx's interactive explainer on lithium and other mood stabilizers.

Clinically, the mechanism is less important than the observed pattern of effects: reduction in manic episodes, prevention of both manic and depressive relapse in bipolar disorder, and reduction in suicide-related outcomes over time.

What to expect starting it

Lithium is dosed by blood level, not by fixed milligrams. Doses are individualized to reach a target serum concentration measured 12 hours after the last dose. Typical target ranges are 0.6 to 0.8 mmol/L for maintenance treatment and 0.8 to 1.2 for acute mania, with individual variation. Starting doses are usually 300 to 600 mg per day, adjusted every few days based on blood level.

Early side effects that often improve over the first weeks: mild tremor, mild nausea, increased thirst, more frequent urination, some cognitive slowing or fogginess. Weight gain is possible and is a common reason people stop the medication.

Side effects that don't tend to improve without dose reduction or a switch: significant tremor, cognitive dulling, prominent GI symptoms, marked polyuria (very frequent urination and thirst), acne or worsening psoriasis.

Time to full effect varies. For acute mania, some response often begins within days, and full stabilization takes a week or two. For maintenance prevention of episodes, the full effect builds over months, and the strongest data on suicide-related outcomes comes from continued treatment over years.

Monitoring

Lithium has a narrow therapeutic window: levels above the target range become toxic. Levels get affected by hydration, illness, kidney function, salt intake, and other medications. Because of this, monitoring is not optional.

Typical monitoring after stabilization: serum lithium level, kidney function (creatinine, eGFR), thyroid function (TSH), and often calcium every 3 to 6 months. More frequent monitoring during dose changes or when medical status changes.

Situations that raise the risk of toxicity: dehydration (from illness, vomiting, diarrhea, sweating, exercise in heat), new NSAIDs (ibuprofen, naproxen), new ACE inhibitors or ARBs (blood pressure medications), new diuretics, low salt intake. Any of those warrant temporary dose reduction or level check.

Signs of lithium toxicity, in order of severity: worsening tremor, GI upset, unsteady walk, confusion, slurred speech, muscle twitches, seizures. Toxicity is an emergency. Call your prescriber or go to an emergency department.

Long-term effects

The two long-term effects that most influence clinical decisions:

• Kidney: chronic lithium use is associated with a gradual decline in kidney function in some people. The decline is usually slow, and severe kidney damage requiring dialysis is uncommon but real. Regular monitoring of creatinine catches problems early.
• Thyroid: hypothyroidism develops in around 20 to 30 percent of people on lithium over time. It's usually easily managed with thyroid hormone replacement and doesn't require stopping lithium.

Other long-term considerations: worsening of pre-existing psoriasis, acne, and some effects on parathyroid function. Weight gain is common. Cognitive effects (a sense of feeling "flatter" or slower) are variable.

Pregnancy and breastfeeding

Lithium in pregnancy is more complicated than for many medications. There's a small increased risk of a specific cardiac malformation (Ebstein's anomaly) when lithium is used in the first trimester. That risk is smaller than earlier estimates suggested, but real. Discontinuing lithium in pregnancy carries its own major risk: relapse of bipolar disorder in pregnancy or postpartum is common and can be severe.

The decision is individualized and involves the person, obstetrics, and psychiatry. Continuing lithium at the lowest effective dose, with monitoring, is often the right choice for someone whose bipolar disorder has been serious and stable on lithium. First-trimester ultrasound and fetal echocardiography are typically arranged.

Lithium in breastfeeding is generally not recommended.

What lithium isn't for

Lithium isn't a first choice for pure unipolar depression without treatment resistance. It isn't an as-needed medication; the dose schedule is fixed. It isn't a substitute for sleep, structure, therapy, and stress management in bipolar disorder; the medication works best when those are also in place.

What tapering off looks like

Stopping lithium abruptly, particularly after long-term use for bipolar disorder, substantially increases the risk of relapse. Tapering slowly over months, when a stop is being considered, is safer. That decision belongs with the prescribing clinician.