SSRI Hyponatremia: What You Need to Know About This Dangerous Side Effect

When you take an SSRI, a class of antidepressants that increase serotonin levels in the brain. Also known as selective serotonin reuptake inhibitors, these drugs include Lexapro, Zoloft, Prozac, and Celexa — and they’re among the most prescribed medications for depression and anxiety. But for some people, especially older adults or those on higher doses, SSRIs can trigger a hidden danger: hyponatremia, a condition where sodium levels in the blood drop too low. This isn’t rare — studies show up to 1 in 10 people on SSRIs develop mild to moderate hyponatremia, and it can turn life-threatening fast.

How does this happen? SSRIs mess with how your kidneys handle water. They cause your body to hold onto too much fluid, which dilutes the sodium in your blood. You might not feel anything at first — but then you get dizzy, nauseous, confused, or even have seizures. Elderly patients, women, and people taking diuretics or with kidney issues are at higher risk. And here’s the catch: many doctors don’t check sodium levels unless symptoms are obvious. That’s why it’s called a silent side effect.

This isn’t just about one drug. It’s about how SSRIs interact with your body’s balance system. If you’re on one of these meds and notice swelling in your legs, frequent urination, or sudden headaches, don’t brush it off. It could be your body screaming for a sodium check. The good news? Most cases reverse quickly once the dose is lowered or the drug is switched. But ignoring it can lead to brain swelling, coma, or worse.

You’ll find real-world case studies and practical guides below that show exactly how this plays out in clinics — from how to monitor sodium levels during treatment, to what alternatives work when SSRIs cause problems. We’ve pulled together posts from doctors, pharmacists, and patients who’ve been through this. No fluff. Just what you need to know to stay safe.