Lithium Side Effects: Tremor, Thirst, Thyroid, and Kidneys

You started lithium and now your hands shake when you hold your coffee, you’re up twice a night to use the bathroom, and you can’t seem to drink enough water. Or maybe your prescriber just mentioned thyroid and kidney blood tests, and you want to know what you’re signing up for.

Lithium is a simple salt that your kidneys handle alongside sodium and water. They filter it, reabsorb much of it, and clear the rest in urine, so hydration, salt, and kidney health all shape how much stays in your blood. It also concentrates in your thyroid gland. Because the gap between a helpful level and a toxic one is narrow, lithium is dosed with precision, using blood tests rather than guesswork.

A 2014 meta-analysis of seven trials with 1,580 participants found that lithium lowered the risk of any new mood episode by about a third compared with placebo, and the authors concluded that no other drug had such ample and consistent evidence for long-term bipolar treatment. The results are real, and the science is well established.

But knowing lithium works doesn’t tell you which side effects are a nuisance you can fix and which are a lab result worth acting on, and at Siggy we think you deserve that distinction before you decide how you feel about the drug.

This guide sorts lithium’s side effects by what they mean: early ones that often ease, slower organ effects that blood tests catch, and signs that point to toxicity. A licensed prescriber can then tie each one to your blood level, hydration, and other medications. That approach treats every side effect as information about your body, and it rests on physiology.

What This Page Covers

• Why Does Lithium Cause Side Effects?
• Which Lithium Side Effects Are Most Common?
• Why Does Lithium Cause a Tremor?
• Why Does Lithium Make You So Thirsty?
• How Does Lithium Affect Your Thyroid and Calcium?
• Is Lithium Bad for Your Kidneys?
• What About Weight, Skin, and Thinking?
• When Is a Side Effect a Warning Sign?
• How Siggy Fits In
• Start Your Anonymous Intake

Why Does Lithium Cause Side Effects?

The FDA lithium prescribing information explains that lithium is completely absorbed, isn’t metabolized, and leaves the body almost entirely through urine. About 80% of what the kidneys filter is reabsorbed. The label puts toxic levels at 1.5 mEq/L or higher, not far above the 0.8 to 1.2 mEq/L range used for acute mania. It also warns that lithium may cause fetal harm, so pregnancy plans belong in the conversation before you start.

Your level shapes your side effects. An international lithium task force recommends a standard maintenance level of 0.60 to 0.80 mmol/L for most adults, with the option to aim lower, 0.40 to 0.60, when lithium is working but hard to tolerate. For lithium, mmol/L and mEq/L are the same number.

Most people notice something. A 2016 review of lithium side effects found that 67% to 90% of people in older studies reported at least one side effect, and most reported more than one.

Which Lithium Side Effects Are Most Common?

Here’s how the most common side effects compare, based on that 2016 review, the FDA label, and the Oxford study discussed below.

Side Effect	How Common	Typical Timing	What Often Helps
Thirst, frequent urination	Up to 70% long term	Early, can persist	Lower level, sugar-free drinks
Hand tremor	About 1 in 4	Usually early	Less caffeine, lower level, propranolol
Nausea	10% to 20%	First weeks	Taking with food, divided doses
Diarrhea	Up to 10%	First 6 months	Level check, rule out toxicity
Weight gain	4.2 kg mean in one 1-year trial	First 1 to 2 years	Low-calorie drinks, early planning
Underactive thyroid	8% to 19% overt	Often early in treatment	Thyroid hormone

Why Does Lithium Cause a Tremor?

Lithium tremor is usually a fine, even shake of the hands that’s most obvious when you hold a position, like writing or lifting a cup. The 2016 review describes it as typically starting early, more common with age, and worse at higher levels. Caffeine and anxiety can add to it.

Simple steps come first: cutting back on caffeine and keeping your level in the low to middle part of the range. If the tremor still gets in the way, beta-blockers such as propranolol are the most common treatment, supported by two small double-blind studies and long clinical experience.

A tremor that turns coarse, spreads beyond your hands, or arrives with vomiting, diarrhea, or unsteadiness can signal toxicity and needs a prompt call to your prescriber.

Why Does Lithium Make You So Thirsty?

Lithium blunts your kidneys’ response to antidiuretic hormone, the signal that tells them to hold on to water. You pass more dilute urine, and thirst follows. The 2016 review reports thirst and frequent urination in up to 70% of people on long-term lithium, though most rate them less bothersome than other side effects.

When the effect is strong, it’s called nephrogenic diabetes insipidus. According to the FDA label, it can develop within weeks of starting, is usually reversible when lithium stops, and may be only partly reversible after long-term use. The label lists amiloride, a diuretic, as an option your prescriber may consider.

Choose water or other sugar-free drinks, since sugary drinks can add to weight gain. Keep your salt intake normal: the label advises a regular diet with salt and roughly 2,500 to 3,000 mL of fluid a day during early stabilization.

How Does Lithium Affect Your Thyroid and Calcium?

Lithium concentrates in the thyroid and can slow the release of thyroid hormone, the label explains. In a Lancet meta-analysis of 385 studies, clinical hypothyroidism was about 5.8 times more likely with lithium than with placebo. Compared with other bipolar medications, the gap is smaller but still real: a 2025 JAMA Network Open cohort of people newly diagnosed with bipolar disorder in Hong Kong found about twice the risk.

An underactive thyroid can look like depression, with fatigue, slowed thinking, weight gain, and feeling cold. The 2016 review reports overt hypothyroidism in 8% to 19% of people on lithium, with higher risk in women, people with thyroid antibodies, and those with a family history. It’s usually treated with thyroid hormone, and the review states it isn’t a reason to stop lithium on its own.

Lithium can also nudge calcium and parathyroid hormone upward. The Lancet meta-analysis found small average increases in both, and the label calls for regular calcium checks because long-term use is linked to hyperparathyroidism. For the full testing rhythm, see our guide to lithium blood levels and kidney and thyroid checks.

Is Lithium Bad for Your Kidneys?

The risk is real, but for most people it’s modest and slow. In the Lancet meta-analysis, lithium cut the kidneys’ urine-concentrating ability by about 15% of normal on average. Kidney filtration fell by about 6 mL/min, a change that wasn’t statistically significant, and 18 of 3,369 patients (0.5%) needed dialysis or a transplant.

Lab-based studies find more chronic kidney disease. An Oxford laboratory study linked lithium to nearly twice the risk of stage 3 chronic kidney disease, with women under 60 and people with higher-than-median lithium levels at greatest risk. The 2025 JAMA Network Open cohort found a smaller increase, 1.35 times the risk of stage 3 or worse, and no increase in advanced kidney disease or kidney failure. More episodes of lithium toxicity were tied to higher risk.

That’s why creatinine and eGFR, a measure of kidney filtration, are checked before and during treatment. The FDA label says progressive or sudden changes, even within the normal range, call for re-evaluation. The 2016 review recommends checks every 6 to 12 months, avoiding toxicity, and keeping levels low in the therapeutic range when possible.

If kidney function does decline, stopping lithium is a planned decision. The review describes fully starting another mood stabilizer first, then tapering lithium over 4 to 8 weeks. Our guide to how lithium doses are set explains why the same dose can land differently over time.

What About Weight, Skin, and Thinking?

The Lancet meta-analysis found people on lithium gained more weight than those on placebo, though less than people on olanzapine. In the 2016 review, patients rated weight gain as the most bothersome side effect, and one double-blind study found an average gain of 4.2 kg over a year.

The label lists skin and hair changes, including folliculitis, new or worsening psoriasis, and hair thinning, though the Lancet meta-analysis found no significant overall increase in skin or hair disorders. The 2016 review treats moderate to severe psoriasis as a relative reason to choose another medication.

A meta-analysis of 12 cognition studies found small but significant effects on immediate verbal memory and creativity, with no significant effect on attention, processing speed, or executive function overall. Long-term use was linked to more psychomotor slowing. Because mood affects thinking too, a prescriber will usually check your level, mood, and other medications before blaming lithium.

When Is a Side Effect a Warning Sign?

Some symptoms shouldn’t be waited out. The FDA label describes toxicity as moving from fine tremor, lightheadedness, poor coordination, and weakness to drowsiness, muscle twitching, unsteadiness, blurred vision, ringing in the ears, and slurred speech, and in severe cases to confusion and seizures. Vomiting and diarrhea can also be signs.

Risk rises with fever, dehydration, heavy sweating, NSAIDs such as ibuprofen, diuretics, and some blood pressure drugs. If you notice these signs, contact your prescriber right away. For confusion, a seizure, fainting, or trouble staying awake, call 911. Our guide to lithium toxicity symptoms covers sick-day precautions in more detail.

Don’t stop lithium on your own because of a side effect. Most can be addressed with your prescriber.

How Siggy Fits In

“No one checks in to see if it’s actually working.” With lithium, the harder question is whether anyone notices a side effect or lab value drifting between visits.

Siggy’s licensed prescribers diagnose and treat the full range of mental health conditions, including bipolar disorder. If you take lithium and also live with anxiety or depression, your full medication list matters: the lithium label warns that combining it with SSRIs and other serotonergic drugs raises the risk of serotonin syndrome. Siggy’s free, anonymous intake takes no name, email, or login, and lets you share your medications, side effects, and recent labs. It gathers structured information and doesn’t diagnose you on its own. A licensed prescriber reviews everything before anything is prescribed, and you get a downloadable summary to bring to the clinician who manages your lithium.

Siggy isn’t an emergency service. If you’re having thoughts of harming yourself, call 911 or call or text 988. This article is for education and isn’t a substitute for advice from your own prescriber. It reflects sources available as of November 2026.

Start Your Anonymous Intake

Lithium’s side effects fall into three groups: early nuisances that often ease, slow thyroid and kidney changes that labs catch, and toxicity signs that need a same-day call. Knowing which is which keeps a treatable side effect from becoming the reason you stop a medication that works, and if lithium truly isn’t a fit, our overview of other mood stabilizers shows the alternatives a prescriber may weigh. Start your anonymous intake with Siggy to share your medications and concerns without your name or email. It’s free, a licensed prescriber reviews your full picture before anything is prescribed, and your summary is yours to keep.