Magnesium needs Vit. C.

Do vitamin C with your magnesium.

If you don't, you might get kidney stones. Which aren't nice, at all at all.

That's preferably a lot more than the paltry 60 mg they're touting as the daily required vitamin C intake up here ... try 2-3 grams of vitamin C with your magnesium.

Your kidneys will thank you.

I don't know the mechanism behind the kidney stones. If you do, please enlighten me. Thanks!

Update, 22 Aug 2014: Ran tells me that vitamin C isn't required, but magnesium is. Here:
"One of magnesium's many jobs is to keep calcium in solution to prevent it from solidifying into crystals; even at times of dehydration, if there is sufficient magnesium, calcium will stay in solution. Magnesium is a pivotal treatment for kidney stones." ["What Really Causes Kidney Stones (And Why Vitamin C Does Not)."Orthomolecular Medicine News Service, 11 Feb 2013.]

Since I wrote the original blog post (above the line ^), I've read up on kidney stones. There are several, and calcium oxalate or calcium phosphate stones are by far the most common (80 % or so of all kidney stones). For those, it's crucial to take magnesium. Magnesium is important to stop calcium stones from forming. Vit. B is important for magnesium to be absorbed. Also, vitamin B6 helps stop oxalate stones from forming. As B-vitamins aren't all that well absorbed on their own, it's best to take a good multi-B. Also take magnesium vinegar:
1 part milk of magnesia
4 parts apple cider vinegar
Mix, let clear (takes about 5 minutes), take 1 tablespoon morning and night.

Luck!