Lithium is one of the oldest and most effective mood stabilizers for bipolar disorder. But it’s also one of the most dangerous if not managed carefully. A tiny change in your body-whether from a common painkiller, a water pill, or even a hot day without enough water-can push lithium levels into the toxic range. This isn’t theoretical. People have died from it.

Why Lithium Is So Sensitive

Lithium doesn’t break down in your body. It’s filtered out by your kidneys, almost entirely unchanged. That means anything that affects how well your kidneys work will change how much lithium stays in your blood. Your kidneys are the gatekeepers. If they slow down, lithium builds up. Even a small dip in kidney function can turn a safe dose into a dangerous one.

The safe range is narrow: between 0.6 and 1.2 mmol/L. Go above that, and you risk toxicity. Below it, and the medication might not work. There’s no room for guesswork. That’s why regular blood tests aren’t optional-they’re life-saving.

NSAIDs: The Silent Risk

Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, naproxen, and diclofenac are everywhere. People take them for headaches, back pain, arthritis. But if you’re on lithium, these can be risky.

NSAIDs reduce blood flow to the kidneys by blocking prostaglandins-chemicals that help keep kidney function steady. Less blood flow means less lithium gets cleared. Studies show NSAIDs can increase lithium levels by 25% to 60%, depending on the drug. Indomethacin is the worst offender, followed by ibuprofen. Celecoxib is a bit safer, but still not risk-free.

The rise in lithium levels usually happens within the first week of taking an NSAID. That’s why many doctors warn against even short-term use. One fatal case in New Zealand involved a 72-year-old woman on lithium and an ACE inhibitor. She took an NSAID for joint pain. Her lithium levels weren’t checked for months. She died from toxicity.

Diuretics: Water Pills That Can Sink You

Diuretics are meant to help your body get rid of extra fluid. But with lithium, they do the opposite-they trap it.

Thiazide diuretics like hydrochlorothiazide are the biggest problem. They cause lithium levels to jump 25% to 50% within 7 to 10 days. That’s fast. And it’s not just a theory. Real patients have ended up in the hospital with tremors, confusion, and vomiting because of this combo.

Loop diuretics like furosemide (frusemide) are less dangerous but still risky. They can raise lithium levels by 10% to 25%. Potassium-sparing diuretics like spironolactone? The data is mixed. Some studies show little effect, others show spikes. Don’t assume they’re safe.

And here’s something most people don’t know: herbal diuretics-those “natural” weight-loss teas or supplements-can be just as dangerous. They’re not regulated. No one checks their strength. But they still cause dehydration and reduce kidney clearance. One case report described a woman who took a “detox” tea and ended up with lithium toxicity.

Dehydration: The Hidden Trigger

You don’t need to be on a drug to put yourself at risk. Just being dehydrated can push lithium into toxic territory.

Lithium floats in your blood. If you lose water-through sweat, fever, vomiting, diarrhea, or just not drinking enough-your blood gets thicker. Lithium concentration rises. Even a 2% to 3% drop in body water can increase lithium levels by 15% to 25%.

This is why travel is a red flag. Flying long-haul? The cabin air is dry. You’re not drinking enough. You’re sitting still. Your kidneys slow down. Lithium builds up. Same with hot weather. If you’re in Perth in summer and you’re out gardening or walking without fluids, you’re playing Russian roulette with your meds.

Even something as simple as skipping salt can make things worse. Your body holds onto lithium when sodium is low. Eat less salt? Lithium goes up. Eat more salt? Lithium goes down. A change of 20-30 mmol of sodium per day can shift lithium levels by 10% to 20%. That’s the difference between safe and toxic.

Who’s at Highest Risk?

Not everyone on lithium is equally vulnerable. Some people are sitting on a ticking clock.

- People over 65: Their kidneys don’t work as well. They’re 3.2 times more likely to have lithium toxicity.

- Those with kidney disease: Even mild chronic kidney disease doubles the risk.

- People with heart failure: Poor circulation means less blood flow to the kidneys.

- Anyone on multiple interacting drugs: Combining NSAIDs, diuretics, and ACE inhibitors? That’s a triple threat.

- Those with poor fluid intake: Whether from forgetfulness, nausea, or fear of frequent bathroom trips, low fluid intake is a silent killer.

What to Do If You’re on Lithium

You don’t have to live in fear. But you do need to be smart.

• Avoid NSAIDs if you can. Use paracetamol (acetaminophen) for pain instead. It doesn’t affect lithium.
• Never start a new diuretic without talking to your doctor. If you’re prescribed one, ask: “Will this interact with my lithium?”
• Drink water daily. Aim for 1.5 to 2 liters, more if you’re active or it’s hot. Don’t wait until you’re thirsty.
• Keep your salt intake steady. Don’t suddenly go low-sodium unless your doctor tells you to. Don’t binge on salty food either-balance matters.
• Get your lithium levels checked after any change. If you start a new medicine, get sick, or travel, ask for a blood test within 7-14 days.
• Know the warning signs. Diarrhea, trembling hands, dizziness, drowsiness, blurred vision, or ringing in your ears? These aren’t just side effects. They’re red flags. Call your doctor immediately.

What Doctors Should Be Doing

Good care means more than just writing a prescription. It means follow-up.

- Lithium levels should be checked weekly for the first month after starting an NSAID or diuretic.

- After that, check every 3 months-or more often if you’re elderly or have other health issues.

- If you’re on long-term lithium, your doctor should monitor your kidney function (creatinine, eGFR) at least once a year.

- Electronic systems should flag interactions. But too often, alerts are ignored. Don’t rely on technology. Talk to your doctor.

The Bottom Line

Lithium works. It saves lives. But it’s not a drug you can take on autopilot. The risks from NSAIDs, diuretics, and dehydration are real, well-documented, and preventable.

You don’t need to avoid all medications. You don’t need to live in a bubble. You just need to be informed. Tell your doctor you’re on lithium before taking anything new-even over-the-counter stuff. Drink water every day. Watch your salt. Know the signs of trouble.

A simple conversation with your doctor and a few lifestyle adjustments can keep you safe. Ignoring them? That’s when things go wrong.