Lithium is widely considered the first-line treatment for bipolar disorder. It has held this position for decades across nearly every major clinical guideline, and it remains the top-ranked option for both acute mania and long-term maintenance. That said, bipolar disorder has distinct phases, and the best first-line choice depends on whether you’re treating a manic episode, a depressive episode, or trying to prevent future episodes altogether.
Lithium’s Role as the Gold Standard
Lithium works across all phases of bipolar disorder. It reduces the intensity of manic episodes, helps with depressive episodes, and is the most proven medication for keeping mood stable over the long term. It also carries a unique benefit that no other mood stabilizer has been shown to match: it reduces the risk of suicide in people with bipolar disorder. This is one of the main reasons guidelines from organizations like the Canadian Network for Mood and Anxiety Treatments (CANMAT) and the International Society for Bipolar Disorders (ISBD) consistently rank lithium at the top.
Lithium does require regular monitoring. Your blood levels need to stay within a specific therapeutic window, typically between 0.6 and 1.0 mEq/L for maintenance treatment, and up to 1.2 mEq/L during acute episodes. Levels above 2.0 mEq/L are potentially dangerous. Because lithium can affect the kidneys and thyroid over time, kidney function is usually checked every two to three months during the first six months, then every six to twelve months. Thyroid function follows a similar schedule.
First-Line Options for Acute Mania
When someone is in a manic episode, the priority is bringing the mood down quickly. The CANMAT/ISBD guidelines rank several medications as first-line for acute mania, listed in order of evidence strength: lithium, quetiapine, divalproex (a form of valproic acid), asenapine, aripiprazole, paliperidone, risperidone, and cariprazine. All of these can be used alone.
For more severe episodes, combination therapy is also considered first-line. This typically means pairing lithium or divalproex with one of the newer antipsychotics like quetiapine, aripiprazole, risperidone, or asenapine. Combinations tend to work faster and more completely than a single medication in severe cases.
Divalproex deserves special mention because it’s one of the most commonly prescribed alternatives to lithium for mania. It works well for acute episodes and is sometimes better tolerated in the short term. The target blood concentration for treating mania is 50 to 125 mcg/mL, and levels are monitored with periodic blood draws, similar to lithium.
First-Line Options for Bipolar Depression
The depressive phase of bipolar disorder is harder to treat than mania, and the first-line options look different. According to CANMAT/ISBD guidelines, quetiapine ranks first for acute bipolar depression, followed by lurasidone (combined with lithium or divalproex), lithium alone, lamotrigine, and cariprazine.
Lamotrigine occupies an interesting spot. It’s one of the most commonly prescribed medications for bipolar depression, but meta-analyses show its effect during acute depressive episodes is modest. One large analysis found it was only slightly better than a placebo for treating active depression. Where lamotrigine truly shines is in prevention: it reduced the risk of future depressive episodes by about 22% compared to placebo and significantly extended the time before depression returned. It was not found to be more effective than lithium for either acute treatment or prevention. So lamotrigine is a strong choice if your bipolar disorder is dominated by depressive episodes and the goal is keeping them from coming back, rather than treating one that’s already in full swing.
Standard antidepressants, the kind used for regular depression, are generally not recommended as first-line treatments for bipolar depression. They can trigger manic episodes or rapid cycling, and they’re only used cautiously, if at all, alongside a mood stabilizer.
Maintenance Treatment to Prevent Relapse
Once an acute episode is under control, the focus shifts to staying stable. This is where first-line treatment becomes especially important, because most people with bipolar disorder will need medication for years or longer. The first-line maintenance options, ranked by evidence, are lithium, quetiapine, divalproex, lamotrigine, asenapine, and aripiprazole. Combinations of these, particularly lithium or divalproex paired with quetiapine or aripiprazole, are also first-line for people who don’t respond fully to a single medication.
The choice between these depends on the pattern of your illness. If your episodes lean heavily toward mania, lithium and divalproex tend to perform best. If depression is the bigger problem, lamotrigine or quetiapine may be more appropriate. Lithium remains the only maintenance medication with strong evidence for reducing suicide risk, which often tips the decision in its favor for people with a history of suicidal thoughts.
Pregnancy Changes the Calculus
For women of childbearing age, the first-line options shift significantly. Valproic acid and divalproex carry the highest risk, with congenital malformation rates of 9% to 11%, including neural tube defects and an increased risk of neurodevelopmental problems in children exposed during pregnancy. Several countries have banned its use in pregnant women entirely, and guidelines recommend avoiding it in anyone who could become pregnant.
Carbamazepine also carries elevated risk, with malformation rates around 3% to 6%. Lamotrigine, by contrast, has a malformation rate of 2% to 3%, which is comparable to the general population baseline. It’s considered the preferred mood stabilizer when bipolar depression is the main concern during pregnancy. Several newer antipsychotics, particularly olanzapine, quetiapine, and aripiprazole, also appear relatively safe, with malformation rates that don’t differ substantially from background rates. Lithium has a relatively low teratogenic risk and can be considered in specific situations, such as when someone has a history of suicidality or has responded well to lithium in the past, though lamotrigine and antipsychotics generally have a better safety profile during pregnancy.
How Treatment Is Typically Chosen
In practice, the “first-line” label doesn’t mean everyone starts on the same medication. Clinicians weigh several factors: which phase of bipolar disorder is most prominent, how severe and frequent episodes are, your medical history, side effect tolerance, and whether pregnancy is a consideration. Someone with classic bipolar I disorder marked by severe manic episodes will often start with lithium or divalproex. Someone with bipolar II disorder, where depression dominates and full mania doesn’t occur, might start with quetiapine or lamotrigine instead.
What “first-line” really means is that these medications have the strongest evidence for working and the best-understood risk profiles. Second-line and third-line options exist for people who don’t respond to or can’t tolerate first-line treatments. Many people with bipolar disorder end up on a combination of medications, particularly if single agents don’t fully control their symptoms. Finding the right regimen often takes time and adjustments, but starting with a proven first-line option gives the best chance of stability from the outset.