Starting Lithium for Bipolar Disorder: What to Know

What should you know before starting lithium?

Lithium is one of the oldest and most studied medicines for bipolar disorder, and the National Institute of Mental Health (NIMH) lists it among the mood stabilizers commonly used to treat the condition. What sets lithium apart from most psychiatric medicines is monitoring: according to the FDA prescribing label, lithium toxicity is closely related to the amount of lithium in your blood, and toxic levels can occur close to the levels that help. That is why your prescriber will order regular blood tests, along with periodic kidney and thyroid labs. Before you start, the practical things to understand are why those labs matter, how hydration and common medicines like ibuprofen can change your lithium level, what the early signs of too much lithium look like, and why you should never stop lithium abruptly without talking to your prescriber first. This article walks through each one, so your first conversation about lithium is informed rather than intimidating.

Why do prescribers still reach for such an old medicine?

Lithium has been prescribed for decades, and it has stayed in use because of what it does: the FDA label lists lithium for the treatment of manic episodes of bipolar disorder and as a maintenance treatment, noting that maintenance therapy reduces the frequency of manic episodes and diminishes their intensity. In plain language, it is used both to bring a manic episode down and to help keep mood more stable over time.

That stabilizing role matters because bipolar disorder involves more than low mood. If you are still sorting out what your own pattern looks like, it can help to read about the difference between bipolar I and bipolar II and when to get help. It is also one reason the depressive episodes of bipolar disorder are approached differently from depression on its own — a mood stabilizer is often part of the plan rather than an antidepressant alone, and that is a decision your prescriber will walk through with you. For a broader picture of the options, including therapy and other medicines, see our overview of how bipolar disorder is evaluated and treated.

Why does lithium need blood tests when most medicines don't?

Most medicines are prescribed at a dose and adjusted based on how you feel. Lithium is different because the gap between a helpful blood level and a harmful one is narrow. The FDA label carries a boxed warning on exactly this point: lithium toxicity is closely related to serum lithium levels and can occur at levels close to therapeutic ones, so prompt blood-level testing should be available whenever lithium is prescribed.

In practice, that means blood draws are not a sign something is wrong — they are how the medicine is used correctly. Levels are typically checked more often when you are starting or when the dose changes, and less often once things are steady, on a schedule your prescriber sets. The timing of the draw relative to your last dose matters for an accurate reading, so follow the instructions you are given about when to take your dose on lab days, and ask if those instructions are unclear.

What are the kidney and thyroid labs actually checking?

Lithium leaves the body through the kidneys, and the FDA label notes that long-term lithium treatment may be associated with reduced kidney concentrating ability and, in some people, changes in kidney function. The label also lists thyroid effects, including hypothyroidism — a thyroid that slows down. Neither of these is a reason to panic; they are the reason your prescriber orders periodic kidney and thyroid blood work, so that any change is noticed early and acted on, rather than discovered late.

It is worth knowing that a slowed thyroid can show up in everyday ways — fatigue, feeling cold, weight change — that are easy to blame on mood or on the medicine itself. Weight changes after starting any psychiatric medicine are worth bringing up — not something to quietly endure. We've written separately about how psychiatric medications can affect weight, including what you and your prescriber can do about it.

Why do water and salt matter so much on lithium?

Your kidneys handle lithium much the way they handle sodium. The FDA label warns that the risk of lithium toxicity rises when the body loses significant salt or water — for example, through heavy sweating, fever, vomiting, diarrhea, or a very low-sodium diet.

What that means day to day: drink water consistently, and treat anything that dehydrates you as a reason to check in. A stomach bug, a long day working outside in the heat, a new intense exercise routine, or a major diet change (including starting a low-salt diet for blood pressure) are all worth a call to your prescriber, because your lithium level can drift even though your dose has not changed. You do not need to memorize the chemistry — you need the habit of mentioning these things.

Which everyday medicines can change your lithium level?

Some of the most important interactions involve medicines people take without thinking of them as medicines. The FDA label states that nonsteroidal anti-inflammatory drugs (NSAIDs) — a category that includes ibuprofen and naproxen — can raise lithium levels. It lists diuretics (water pills) and certain blood pressure medicines, such as ACE inhibitors, as able to do the same.

The practical rules are simple. Tell every clinician and pharmacist you see that you take lithium, including dentists and urgent care providers. Before taking an over-the-counter pain reliever, ask your prescriber or pharmacist whether it is safe with lithium and whether another option would be better for you. Any time a doctor starts or adjusts a blood pressure medicine or a diuretic, tell whoever manages your lithium — your level may need to be rechecked.

What are the early signs of too much lithium?

According to the FDA label, early signs of lithium toxicity can include diarrhea, vomiting, tremor, mild unsteadiness, drowsiness, and muscle weakness. If you notice symptoms like these — especially after being sick, dehydrated, or starting a new medicine — hold off on your next dose and contact your prescriber right away for instructions. Severe symptoms such as confusion, marked unsteadiness, or slurred speech are a reason to seek emergency care, not to wait for a callback.

And a separate but important point: if you ever have thoughts of suicide or self-harm, whether or not you take lithium, call or text 988 to reach the 988 Suicide & Crisis Lifeline, available 24 hours a day, or go to the nearest emergency room.

Why shouldn't you stop lithium on your own?

Feeling well on lithium often means the medicine is doing its job, and stopping it — especially suddenly — removes that protection. If side effects, cost, lab fatigue, or simply wanting to be off medication are on your mind, bring it to your prescriber as a plan to discuss rather than a decision already made. If stopping turns out to be right for you, your prescriber can do it deliberately, with a plan for watching your mood along the way.

Missing a single dose is a different situation from quitting, but it has its own rules — doubling up is not automatically the answer. We cover that in what to do when you miss a dose of a psychiatric medication.

What should you ask at your first appointment?

The most useful lithium conversations get specific. A few questions worth bringing along:

• How often do you check my lithium level, kidney function, and thyroid — and where do I go for the blood draws?
• If I'm sick one day — vomiting, sweating heavily — what should I do?
• Which over-the-counter pain relievers are safe for me?
• If I'm on a blood pressure medicine or water pill, or end up needing one, what does that mean for my lithium?
• What do I need to know if I'm pregnant, or could become pregnant? (The FDA label warns that lithium may cause fetal harm, so this is a conversation to have early, not after the fact.)
• What symptoms mean I should call you, and what symptoms mean I should go to the ER?

If anxiety is also part of your picture — and it often travels with mood disorders — mention it, because treating anxiety can run alongside a mood-stabilizer plan rather than waiting behind it. The psychiatric clinicians on our team have these conversations every day, and questions about coverage for visits and lab work are answered on our insurance page. When you are ready to talk it through with a prescriber, you can book an appointment.

Frequently asked questions

How long does it take lithium to start working?

It varies by person and by what lithium is being used for — calming a manic episode is a different timeline from long-term maintenance. Rather than a one-size-fits-all number, ask your prescriber what to expect in your situation and when you will reassess together. Early blood tests are partly about finding the level that works for you, so the first weeks are an adjustment period by design.

Will I need blood tests for as long as I take lithium?

Monitoring continues for as long as you take lithium, because the FDA label ties lithium's safety directly to blood levels. The frequency usually changes over time, though: levels are checked more often at the start and after dose changes, and less often once you are stable, on a schedule your prescriber sets.

Can I take ibuprofen for a headache while on lithium?

Ask before you do. The FDA label states that NSAIDs such as ibuprofen and naproxen can raise lithium levels. Your prescriber or pharmacist can tell you whether a different pain reliever is a better choice for you, and what to do if you have already taken one.

What happens if I get dehydrated?

Losing salt and water — through illness, heat, fever, or heavy exercise — can raise your lithium level even though your dose has not changed, which the FDA label flags as a risk for toxicity. Drink fluids, and contact your prescriber if you have been vomiting, have diarrhea, or notice symptoms like tremor, unsteadiness, or unusual drowsiness.

Is it safe to take lithium while pregnant or trying to conceive?

The FDA label warns that lithium may cause fetal harm, so pregnancy — current or planned — is something to tell your prescriber about as early as possible. Do not stop lithium on your own if you learn you are pregnant; call your prescriber the same day so you can weigh the risks of the medicine against the risks of an untreated mood episode together.

Can I ever come off lithium once I start?

Starting lithium is not a life sentence, but stopping is a medical decision, not a solo one. If you want to come off it, say so — your prescriber can talk through timing, taper the medicine deliberately if stopping is appropriate, and plan how you will both watch for returning symptoms. Stopping abruptly on your own is the one approach every prescriber will ask you to avoid.

This article is for educational purposes only and is not medical advice, a diagnosis, or a substitute for care from a licensed clinician. In a crisis, or if you're having thoughts of suicide, call or text 988 to reach the 988 Suicide & Crisis Lifeline — or go to the nearest emergency room.