@rbusch1944 Are you taking this much because a doctor told you to do it for a specific reason? Or from something you read? Keep in mind that chronic diarrhea can deplete a lot of nutrients in your body, so it is not something to "just live with."

If you are not under doctor's orders, perhaps you can research foods rich in magnesium and add as much as possible to your diet. Then take a VERY small amount as a supplement - there are tablets as small as 100mg, and even these can be divided.

If you are under doctor's orders, discuss whether you can do this with them. Maybe keep a food diary to show how you have increased your consumption.

Here is a list of magnesium-rich foods:
https://health.clevelandclinic.org/foods-that-are-high-in-magnesium
And here is a more comprehensive list you can research:
https://www.careomnia.com/nutrition-tool-nutrient
Here is how I get at least 400 mg of magnesium from my diet:
Breakfast: Coffee with 1c milk (90mg +25 mg)
Greek yogurt with a banana or raspberries & a handful of pumpkin seeds: (40mg+30mg+150mg)
Or buckwheat pancakes + peanut butter (40mg+100mg)
Lunch: Avocado on crackers (I cannot eat wheat so I substitute) (58mg+40mg)
Or hummus on crackers (24mg+40mg)
Or peanut butter on gluten-free whole grain bread: (100mg+20mg)
Snack: Cashews (70mg)
Dinner:
Baked potato with skin topped with cheddar (42mg+7mg)
OR boiled sweet potato (70mg)
OR baked squash (80mg)
OR bean soup (150mg+)
OR chili with meat and beans (30mg+70mg)

So you can see, the choices are many!

Another was to lessen symptoms is to take the magnesium in divided doses throughout the day, on a full stomach after a meal to "dilute" its effect. This is not something that needs to be taken all at once or on an empty stomach.

@rbusch1944 Which formulation are we discussing in your case? If it's the common, and most efficiently uptaken, citrate salt, then 500 mg is obviously too much for your system, and you should advise your physician who prescribed that dose of your experience. If you take 500 mg of bis-glycinate, and it's too much, then maybe you should back off the dose or try yet another salt...malate or taurate maybe? But do run this past the prescribing physician.

@rbusch1944 ..Hi..magnesium glycinate should NOT give you diarrhea..it is magnesium citrate that may do that

@rbusch1944
I would not increase your OTC without approval from your doctors. It is just good to have medical advice on OTC supplements if you are taking medications and other supplements. I am on 16 different medications and several OTC supplements.

You asked about how to prevent diarrhea. What type magnesium are you taking? Citrate can cause diarrhea in many people. It is why a lot of doctors will recommend Glycinate as does not cause this. I do not have a problem taking Citrate. However, I split the type and take 200 mg of Citrate and 200 mg of Glycinate.

I read on many medical institutions the various forms of magnesium have specific added benefits. The Citrate is overall good for the PVCs, PACs, etc. but the Taurine is good for tachycardia, and Citrate is good for them (PACs, PVCs,) but also helps with digestion. I may add the taurine also and lower my citrate intake.

I want to pass on that every OTC I take is with the approval of my doctors. I do not take anything without their approval. I learned a lot by not doing so you could be doing yourself harm and not know it. Many things aggravate a condition, contradict a medications, or interfere with absorption etc. One of the main OTC is grapefruit. An OTC or eating it. My doctors say can really cause a higher degree of some medications therapeutics.