Question: What measurement of magnesium status is best to use for arrhythmias?I assume by "measure" you mean a measurement of nutritional status, in which case I think you want to look at the serum level. think that if you're trying to fix a problem with the serum level, you probably at some point want to look at the red blood cell level and the urine level. One of the ways that magnesium could impact the arrhythmias would be through influencing other minerals, and so I would not recommend just looking at magnesium on its own. You definitely have to look at the calcium levels, the sodium levels, the potassium levels, and those would be the big four. . This Q&A can also be found as part of a much longer episode, here.  If you would like to be part of the next live Ask Me Anything About Nutrition, sign up for the CMJ Masterpass, which includes access to these live Zoom sessions, a private discussion group, premium features on all my content, and hundreds of dollars of exclusive discounts. You can sign up at https://chrismasterjohnphd.com/masterpass/ and use the code QANDA to get 10% off the membership for life. There are two ways to discuss this episode: Discuss it in The Masterpass FREE Forum, which is freely open to everyone, at https://chrismasterjohnphd.com/discuss  If you’re a Masterpass member, discuss it in the Masterpass Discussion Group, found in your dashboard. DISCLAIMER: I have a PhD in Nutritional Sciences and my expertise is in performing and evaluating nutritional research. I am not a medical doctor and nothing herein is medical advice.