When you’re taking lithium, a mood-stabilizing medication commonly prescribed for bipolar disorder. Also known as lithium carbonate, it helps keep emotions from swinging out of control—but it doesn’t come without trade-offs. One of the most common and often overlooked side effects? Thyroid trouble. Many people on long-term lithium don’t realize their fatigue, weight gain, or brain fog might not be part of their mental health condition—they could be signs their thyroid is slowing down.
Thyroid management on lithium, the process of monitoring and treating thyroid dysfunction caused by lithium use. Also known as lithium-induced hypothyroidism, it’s not rare—it happens in up to 20% of people who take lithium for more than a year. Your thyroid doesn’t stop working all at once. It creeps up slowly. You might feel tired all the time, gain weight without changing your diet, get cold easily, or notice your memory isn’t as sharp. These aren’t just "bad days." They’re signals your body’s metabolism is slowing because lithium interferes with how your thyroid releases hormones.
Doctors don’t always check thyroid levels when you start lithium, and even when they do, they might wait too long to act. That’s why you need to be your own advocate. Get a simple blood test—TSH, free T4, and sometimes free T3—every 6 to 12 months, or sooner if symptoms show up. If your TSH is high and T4 is low, you likely have hypothyroidism. The good news? It’s usually easy to fix with a daily pill: levothyroxine, a synthetic form of thyroid hormone used to replace what your body isn’t making. Also known as Synthroid, it’s safe, cheap, and doesn’t interfere with lithium’s mood-stabilizing effects. You can keep taking lithium and still feel like yourself again.
Some people worry that starting thyroid medication means they’re failing or that their lithium isn’t working. That’s not true. This isn’t a sign your treatment failed—it’s a sign your body responded to the drug, and now you’re managing the side effect. Many patients stay on lithium for decades and only need thyroid support to feel normal. It’s not weakness. It’s smart care.
And if you’re wondering whether you should stop lithium because of this? Don’t rush. Stopping lithium abruptly can trigger a manic or depressive episode. The goal isn’t to avoid lithium—it’s to manage it well. That means regular blood work, paying attention to how you feel, and working with a doctor who understands the connection between mood meds and thyroid health.
Below, you’ll find real-world guides on how to spot early signs of thyroid trouble, what tests actually matter, how to talk to your doctor about it, and how to safely combine lithium with thyroid medication. No fluff. No jargon. Just what works for people who’ve been there.
