When you take lithium, a mood-stabilizing medication commonly prescribed for bipolar disorder. Also known as lithium carbonate, it helps prevent extreme mood swings—but it doesn’t come without risks. One of the most common and serious side effects is how it messes with your thyroid, a small gland in your neck that controls metabolism, energy, and mood. Many people don’t realize this until they start feeling tired, gain weight, or feel depressed—even when their bipolar symptoms are under control. That’s because lithium can cause hypothyroidism, where your thyroid doesn’t make enough hormones. It’s not rare. Studies show up to 20% of people on long-term lithium develop some form of thyroid problem.
The good news? You can catch it early with simple blood tests. Thyroid function test, a basic lab panel that measures TSH, T3, and T4 levels. Your doctor should check this before you start lithium, then every 6 to 12 months after. If your TSH rises above normal, it’s a red flag. You might need a low-dose thyroid pill like levothyroxine, which works fine alongside lithium. Skipping these tests is like driving with your eyes closed—you might be fine for a while, but something bad is waiting to happen.
It’s not just about feeling sluggish. Untreated thyroid issues can make your mood worse, increase your risk of heart problems, and even reduce how well lithium works. Some people think if they feel okay, they don’t need the test. But thyroid problems don’t always come with obvious symptoms. That’s why regular monitoring isn’t optional—it’s part of safe, long-term treatment. And if you’re on lithium, you’re not alone. Thousands of people manage both their bipolar disorder and thyroid health without issues, as long as they stay on top of blood work.
You’ll also want to watch your salt and fluid intake. Too little salt or dehydration can spike your lithium levels, which increases the chance of toxicity. Drink water regularly, avoid extreme diets, and tell your doctor if you start taking new meds—some painkillers, diuretics, and even NSAIDs can interfere. The goal isn’t to scare you, but to empower you. Lithium works. But it only works safely when you’re informed and proactive.
Below, you’ll find real-world guides that dig into how lithium affects your body, what blood tests to ask for, how to talk to your doctor about side effects, and what alternatives exist if your thyroid doesn’t respond well. These aren’t theory pages—they’re practical, tested advice from people who’ve been there. You don’t need to guess. You just need to know what to look for.
