Lithium Interactions: NSAIDs, Diuretics, and Dehydration Risks Explained

Take lithium for bipolar disorder? You might think your medication is stable - but a simple cold, a new painkiller, or even skipping a few glasses of water could push your lithium levels into dangerous territory. This isn’t hypothetical. People on lithium have ended up in the hospital - some fatally - because of interactions with common drugs or everyday habits. The truth? Lithium is powerful, but it’s also fragile. Even small changes in your body or meds can tip the balance. Lithium works by stabilizing mood, but it doesn’t take much to turn it from a lifesaver into a threat. Its therapeutic range is incredibly narrow: between 0.6 and 1.2 mmol/L. Go just a little above that, and you risk nausea, tremors, confusion, or worse. Go much higher, and you could have seizures, kidney damage, or even die. And here’s the kicker: you might not even feel sick until it’s too late. The biggest culprits? NSAIDs, diuretics, and dehydration. These aren’t rare or exotic risks. They’re part of everyday life. Millions of people take ibuprofen for back pain. Older adults use hydrochlorothiazide for high blood pressure. Everyone gets sick, travels, or forgets to drink water sometimes. But for someone on lithium, these aren’t harmless choices. They’re red flags. NSAIDs: The Silent Lithium Booster Nonsteroidal anti-inflammatory drugs like ibuprofen, naproxen, and celecoxib are everywhere. You grab them for a headache. Your doctor prescribes them for arthritis. But if you’re on lithium, they’re not just painkillers - they’re lithium elevators. NSAIDs reduce how well your kidneys clear lithium. They do this by blocking prostaglandins, which help maintain blood flow to the kidneys. Less blood flow = less lithium filtered out = more lithium building up in your blood. Studies show NSAIDs can raise lithium levels by 25% to 60%, depending on the drug. Indomethacin is the worst offender - it can spike levels by up to 60%. Ibuprofen? Around 25-40%. Celecoxib is a bit safer, but still risky. The rise doesn’t happen overnight. It usually kicks in within a week of starting the NSAID. That’s why many people don’t connect the dots. They take Advil for a few days after a sprained ankle, feel a little off, and blame it on the injury - not the pill. The risk is highest in older adults, especially those over 65. Their kidneys don’t work as well to begin with. Combine that with NSAIDs and lithium, and you’ve got a perfect storm. One fatal case in New Zealand involved a 72-year-old woman on lithium and an ACE inhibitor. She started taking an NSAID for joint pain. Her lithium levels weren’t checked regularly. She died from toxicity. Diuretics: Water Loss, Lithium Gain Diuretics are called water pills. They help your body get rid of extra fluid. That’s why they’re used for high blood pressure and swelling. But lithium is also cleared by your kidneys - and it rides along with water. When diuretics pull out water, they pull out lithium too… right? Not exactly. Thiazide diuretics - like hydrochlorothiazide - are the real problem. They don’t just increase urine output. They change how your kidneys handle sodium and lithium. Instead of flushing lithium out, they reabsorb it. The result? Lithium levels jump by 25-50% within 7 to 10 days. That’s a huge spike. Loop diuretics like furosemide are less dangerous, but still risky. They can raise lithium levels by 10-25%. Potassium-sparing diuretics like spironolactone? The data is mixed. Some studies show little effect. Others show dangerous rises. Don’t assume they’re safe. And here’s something most people don’t know: some diuretics actually lower lithium levels. Osmotic diuretics like mannitol and carbonic anhydrase inhibitors like acetazolamide can reduce lithium concentrations by 15-30%. That’s not a good thing either. If your dose was carefully tuned for your normal levels, a sudden drop could trigger a return of mood symptoms. Even herbal diuretics - the ones sold as “natural” weight-loss aids - can be dangerous. They’re not regulated. People think they’re harmless. But they can cause dehydration and lithium spikes just like prescription pills. Dehydration: The Invisible Trigger You don’t need a drug to raise your lithium levels. Just lose water. Lithium is dissolved in your blood. When you’re dehydrated, your blood gets thicker. That means the same amount of lithium is packed into less fluid - so concentration goes up. Even mild dehydration - losing just 2-3% of your body weight in water - can push lithium levels up by 15-25%. Think about it: you get the flu. You can’t keep food or water down. You’re sweating from a fever. You take a long flight. You’re in a hot climate. You work out hard and don’t rehydrate. All of these situations can trigger lithium toxicity - even if you haven’t taken a new pill. One study found that 68% of early lithium toxicity cases included diarrhea. That’s not a coincidence. Diarrhea = fluid loss = lithium rise. Same with vomiting, fever, or excessive sweating. The NHS Borders guidelines are blunt: “It is important to keep taking lots of fluid especially in situations where there is risk of dehydration and increased loss of salt, eg after exercise, long distance air travel, sickness, fever, diarrhoea.” And it’s not just about drinking water. Sodium matters too. If you suddenly eat less salt - say, you go on a low-sodium diet - your body holds onto lithium. That can raise your levels by 10-20%. Conversely, if you eat more salt, your kidneys flush out more lithium. That can make your mood unstable. Consistency is key. Who’s Most at Risk? Not everyone on lithium will have a bad reaction. But some people are walking into danger without knowing it. - People over 65: Kidney function declines with age. Older adults are 3.2 times more likely to experience lithium toxicity. - Those with kidney disease: Even mild kidney impairment makes lithium clearance harder. - People with heart failure: Fluid balance is already off. Adding diuretics or NSAIDs makes it worse. - Those on multiple medications: The more drugs you take, the higher the chance of a bad interaction. - Travelers or people in hot climates: Heat + dehydration = high risk. What Should You Do? If you’re on lithium, here’s your action plan:

• Avoid NSAIDs if possible. Use acetaminophen (Tylenol) for pain instead. It doesn’t affect lithium.
• Never start a diuretic without telling your doctor. If you need one, your lithium dose may need to be lowered - and you’ll need weekly blood tests for at least a month.
• Drink water daily. Aim for 8-10 glasses, more if you’re active, sick, or in the heat. Don’t wait until you’re thirsty.
• Don’t change your salt intake suddenly. Keep your diet consistent. No extreme low-sodium diets without medical supervision.
• Know the early signs of toxicity: Diarrhea, nausea, tremors, dizziness, drowsiness, blurred vision, or ringing in the ears. If you feel any of these, stop the NSAID or diuretic and call your doctor immediately.
• Get your lithium levels checked regularly. Even if you feel fine. Your doctor should check levels every 3-6 months - and always after starting or stopping any new medication.

What If You Need the Medication? Sometimes you can’t avoid NSAIDs or diuretics. Maybe you have severe arthritis. Maybe you have heart failure. In those cases, don’t stop your lithium - but do this:

• Work with your doctor to lower your lithium dose before starting the other drug.
• Get your lithium level checked within 5-7 days after starting the new medication.
• Check again after 2 weeks, then monthly until stable.
• Use the lowest effective dose of the NSAID or diuretic for the shortest time possible.
• Keep a symptom diary. Note any changes in energy, coordination, or digestion.

Why This Isn’t Just a ‘Warning’ - It’s a Lifesaver This isn’t about being careful. It’s about survival. Lithium toxicity doesn’t always come with a siren. It creeps in. A little more fatigue. A bit more shakiness. A bit more confusion. You think it’s stress. Or aging. Or the flu. But it’s your lithium level climbing - slowly, silently - toward danger. The good news? This risk is predictable. It’s well-documented. It’s avoidable. You don’t need to live in fear. You just need to know what to watch for. Your lithium isn’t broken. It’s just sensitive. Treat it like a precision instrument - not a blunt tool. Keep your fluids up. Avoid the risky meds unless absolutely necessary. Talk to your doctor before adding anything - even over-the-counter pills or herbal supplements. Because when it comes to lithium, the difference between stability and crisis isn’t always a big change. Sometimes, it’s just one pill - or one day without enough water. Final Thought: If you’re on lithium, your health team should be your partner. Don’t be afraid to ask: ‘Could this drug or habit affect my lithium?’ That question could save your life.