The Magnesium Question

The mineral everyone's talking about — and what the evidence actually shows.

I think half of the patients I saw yesterday asked me about magnesium. It has overtaken vitamin D as the supplement most likely to come up in a primary care visit, and the questions have grown more specific over time. Not should I take magnesium, but how much, should I take glycinate or threonate, or does 400 milligrams work for sleep? Anxiety? I often learn about online health trends not so much by being online, but by being in the real life examining room with twenty patients a day. And so in this post I’ve researched and then synthesized a thorough answer, full of conventional wisdom and overlooked ideas. Let’s review what’s up with magnesium in our bodies, what the evidence actually supports, why a serum magnesium blood test might be misleading, the different formulations, dietary versus supplementation sources, side effects, and how to do magnesium well if we’re going for it.

This is the world we practice in now. A recent industry survey found that doctor recommendations and social media are the top sources patients use for supplement information. Another survey from Pew Research Center found that 75% of Americans most highly value medical training, transparency about conflicts of interest, and ease of understanding… with health care providers rated highest (even above AI for now). So here is the best I can do for magnesium. The version I would give in the office if only I had more time. I make no money from commissions or selling stuff.

The strongest case for supplementing is with genuine magnesium deficiency. Certain people are far more prone to it than the general population, where low magnesium levels still run about 3–10%. Antacids like omeprazole cause deficiency in roughly 20% of long-term users, and diuretics used for treating conditions like high blood pressure waste magnesium through the kidney. Poorly controlled type 2 diabetes (10–30% prevalence), alcohol use disorder, and chronic diarrhea or malabsorption are classic culprits, as are certain chemotherapies and older folks on five or more medications. If you fit one of these, the conversation shifts from wellness trend to genuine medicine. Nonetheless, we will briefly review the evidence for magnesium and sleep, migraines, blood pressure, insulin sensitivity, cognitive function, anxiety, and muscle cramps to name a few.