Managing Lithium-Induced Thyroid Issues: What You Need to Know

When you're taking lithium, a mood-stabilizing medication commonly used for bipolar disorder. It's one of the most effective treatments for preventing extreme mood swings, but it doesn't come without trade-offs. One of the most common, and often overlooked, side effects is its impact on your thyroid, a small gland in your neck that controls metabolism, energy, and body temperature. About 1 in 5 people on long-term lithium develop some form of thyroid problem—usually hypothyroidism—where your thyroid doesn’t make enough hormones. That means you might feel tired all the time, gain weight without trying, get cold easily, or struggle to focus. These symptoms don’t always show up right away, and they’re easy to blame on stress or aging. But if you’re on lithium, they could be your body signaling a real issue.

It’s not just about feeling sluggish. Left untreated, lithium-induced thyroid problems can make your mood swings worse, reduce how well lithium works, or even lead to heart issues over time. That’s why regular blood tests aren’t optional—they’re essential. Your doctor should check your TSH, thyroid-stimulating hormone, the main indicator of thyroid function. levels at least once a year, and more often when you first start lithium or if your dose changes. If TSH is high, it means your thyroid is struggling. In many cases, adding a simple daily dose of levothyroxine, a synthetic thyroid hormone used to replace what your body can’t make. fixes everything without stopping lithium. You don’t have to choose between mental health stability and physical health—you can have both.

What makes this tricky is that not all doctors check for it. Some assume you’ll notice the symptoms yourself. Others think it’s too common to worry about. But if you’re on lithium, you need to be your own advocate. Ask for your TSH and free T4 numbers every time you get blood drawn. Keep a log. If your energy drops, your weight creeps up, or your mood feels off for no reason, bring it up. Lithium isn’t going anywhere for most people—it’s a lifeline. But your thyroid needs attention too. The good news? This isn’t a crisis. It’s a manageable side effect. With the right monitoring, you can keep taking lithium safely, without letting your thyroid slow you down.

Below, you’ll find real-world advice from people who’ve been there—how to spot early signs, what questions to ask your doctor, and how to avoid the most common mistakes when managing this side effect.