Is Magnesium Dangerous for the Kidneys?

Dear Friends,

I must apologise for not being on NOF for some time. It was only because I had nothing of importance to add, and there were already persons with very good knowledge writing here.

However lately I have woken up to the fact that lots of people are taking Magnesium up to 300 mg or more these days for better health. Yet when I go to study any site on Magnesium -- and in fact even when I look at the various drug advertisments on Magnesium, one thing worries me, even for small amounts like 100 mg or 160 mg.

Almost all of the drug companies say that Magnesium should not be taken by people who have any degree of kidney trouble. There are even sites that say that Magnesium can be bad for the elderly whose kidneys are functioning slowly.

And there was even a site which said that Magnesium could even harm a healthy kidney and cause it to go into failure. This is because Magnesium is one of those substances that needs to pass out through the kidneys -- and if the kidneys are not doing a good job it can accumulate there.

This means that every time we start Magnesium, or have been taking Magnesium for some time, we must get our kidneys checked for creatinine and creatinine clearance and glomular filtration rate GMR -- in other words we must get our kidney functions checked, before and after starting Magnesium.

This seems alarming to me. Because I am not accustomed to getting the kidneys checked each time I start any supplement. I suppose ideally we should all get kidney functions tests done before we embark on any multivitamin mineral tablets. Kidney disease creeps up on a person insidiously, he does not know that he has it till the symptoms become pronounced, like swelling in the face and legs etc. Even a small thing like a urinary infection is enough to start off a kidney infection, and many people are not aware of it till in the late stages.

So -- the question arises, no matter how great the benefits of supplements to the health and the bones, we have to consider the damage that they can do to the kidneys -- something that can be irreversible. Having a kidney transplant does not appear to be a very palatable alternative. And if one is forced to do that just for the nebulous "benefits" of the supplement it would be quite tragic.

It is indeed good that the manufacturing companies have themselves stated the dangers of Magnesium to the kidneys. So should we be taking it at all as a supplement in the form of a tablet at doses of even 100 mg far less 300 mg and more?

I suppose members on NOF would best be able to explain the situation if they have been taking Magnesium themselves in large quantities over 100 mg. How many people got their kidney functions tested before and after starting Magnesium?

Best wishes and warm regards,
I remain,
Yours, as ever,

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60 replies. Join the discussion

Hello Priya

It's so good to hear from you. Your posts are always helpful.

I hadn't heard about this before and I have been massaging magnesium oil all over every day. I wonder if this method also affects the kidneys. It is said we absorb very little magnesium taken in capsule or tablet form.

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Hello Priya,
I have been thinking of you, and glad to see you here again.
You always bring up such great topics.

I have been thinking the samething about all the vitamins I have been taking. Thinking they might be hard for my Kidneys to process!

Three weeks ago, I told my Dr, I wanted allot of tests taken.
He called me the day after taking them, to say he only got back the urine test and I had a raging bladder infections!
How can that be, I did not have any symtoms!! But I have been having pain on the lower right side of my back, and right side near my liver.
That said, my ankles that are skinny have been swelling up for some time now.
Last year I was sent to the cardio dr. went for a coroided (sp?) artery test, and everything showed I have great circulations.
I could not get a answer from any of those drs about the swollen ankles, but I have been searching the net before taking all the tests, and I said to the Dr. I think I have a Kidney problem. He thought I was crazy lol ..
I went on antibiotic for 12 days, for the bladder infections, which is also a antibiotic for kidney infections.
My ankles are no longer swollen even if I put salt on my food, which I very rarely do, cause they would swell up. (besides do not think salt is healthy)
I have been thinking, all the vitamins I take are allot for my kidneys to process.
Glad you brought this up, as it could be the Mag I'm taking that was causing the problem!!
Do you think by eating foods with magnesuim, would not cause a kidney problem? Instead of taking the magnesium vitamin?

Sorry to make a short story , long!

Be well,

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Wow. I started magnesium a couple of months ago. Glad I saw this post. I will stop. I take cranberry pills for my bladder (started before the magnesium). Do you know of any harm that can be created by taking these?


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Hiya, Priya: Long time no hear.
For you others, have your doctor do a simple urine sample at your next physical. If you have kidney problems, you'll know it. However, RDA of magnesium for women is about 340, for men about 420. (That's mg, folks. I can't remember the exact dosage.) You should be safe with 100 to 250mg per day.

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I think we should remind readers first of the importance of magnesium by reading what a Nephrologist (expert in kidney function) has to say on the topic.
Nephropal on Magnesium

Dr BG also has a useful post showing the importance of correcting magnesium deficiency

Bear in mind we live in a world where
Magnesium, inflammation, and obesity in chronic disease. 60% of adults in the United States do not consume the estimated average requirement for magnesium.... low magnesium status has been associated with numerous pathological conditions characterized as having a chronic inflammatory stress component......significance in obesity, which is characterized as having a chronic low-grade inflammation component and an increased incidence of a low magnesium status. Marginal-to-moderate magnesium deficiency through exacerbating chronic inflammatory stress may be contributing significantly to the occurrence of chronic diseases such as atherosclerosis, hypertension, osteoporosis, diabetes mellitus, and cancer.</A>

We should also bear in mind that most people (particularly in the USA but increasingly elsewhere) have excessive levels of omega 6 in relation to omega 3. in rats omega 6 leads to magnesium excretion and omega 3 improves retention. this may be particularly important for most readers here.

Does a higher ratio of serum calcium to magnesium increase the risk for postmenopausal breast cancer?

Krispin has more basic information about using a sensible amount of magnesium supplement

Bear in mind Magnesium deficiency is a relatively common condition while risk of adverse effects is very low While it is possible to find examples of magnesium toxicity from laxative abuse and during hospital treatments these are at EXTREMELY high intakes totally unrelated to the modest amounts suggested for the correction of magnesium deficiency.

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Does anyone if mg oil put on one's skin can affect the kidneys?
My kidney function is lower than normal and I don;t wnat to exacerbate is further.

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In this article it states mg oil does not affect the kidneys

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I think the benefits of magnesium supplementation outweigh any possible ill effects. I am taking 315 mg of magnesium/day in powder form split into 2. By mistake on the first day and in a hurry I took 630 mg in one dose which caused slight diarrhea. There is a useful site: which discusses certain vitamins/minerals/drugs and their potential benefits/side effects.

I like the idea of using magnesium transdermally and think it was Ted who mentioned you can buy large bags of magnesium chloride - is that correct? If you added water to measured amounts of mg chloride could it then be used as an oil to rub on the skin - (possible skin reactions)? Also if it is better absorbed through the skin I presume you need to use less than you would in powder or pill form.

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I have been taking 750 mg of magnesium every day.
I thought we had to take about half of the calcium.
Am I wrong?
I also got the magnesium oil to apply on the skin, but when I use it I don't take so many pills.
I am confused now.

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I have been taking magnesium for about 5 years, 300mg per day. I have had my kidneys checked every 6months all that time and they havent altered at all, in fact the last time the function was better.

Very confusing, but then everyone is different.

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I personally do not think anyone needs to take 1500mg calcium.
I think between 1000~1200mg is sufficient BUT even then food sources and water should be the major source. So rather than supplement with 1200mg/calcium daily I would try to increase daily calcium intake from my food water and other beverages so more than 600mg daily was available and I would restrict daily calcium to no more than 600 mg from supplements per day.

Because modern shorter faster maturing grain varieties contain less magnesium than just 50yrs ago we do need MORE magnesium from supplements than previously thought necessary.
Krispin's suggestion is a total of
5 to 10 milligrams per day per kilo of ideal body weight or 2.5 to 4.5 milligrams per day per pound of ideal body weight.

Example: 70 kilos or 150 pounds= 350 mg. to 700 mg. daily.

But this is TOTAL intake and you also need to do your diet sums and check your water supply to see how your diet sources add up and then use supplements to make up the difference.

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@ Very confusing, but then everyone is different.
Indeed, but THE VAST MAJORITY of people are currently magnesium deficient. So we really only need to worry about the potential for overdose AFTER we have ensured the majority of people at least meet the current (albeit too low) RDA.

Our IMMEDIATE major problem is raising the average daily magnesium intake in the face of lower nutrient levels resulting from faster crop turn over from newer grain varieties and possibly faster excretion levels of magnesium.

Only those people with KIDNEY FAILURE will not be able to handle excess magnesium.

Remember our DNA evolved when food sources of magnesium were higher (magnesium is water soluble so over the 3.4million yrs human types evolved much of that magnesium has ended up in the sea) and now higher omega 6 intakes over the last 50yrs results in magnesium being lost in urine as higher acidic diets allow calcium to be leached out.

High magnesium intake is associated with lower concentrations of certain markers of systemic inflammation (CRP, IL-6, TNF-alpha, VCAM) and endothelial dysfunction in postmenopausal women.

Elevated brain levels of magnesium enhance learning and memory
"Our findings suggest that elevating brain magnesium content via increasing magnesium intake might be a useful new strategy to enhance cognitive abilities," explains Dr. Liu. "Moreover, half the population of industrialized countries has a magnesium deficit, which increases with aging. This may very well contribute to age-dependent memory decline; increasing magnesium intake might prevent or reduce such decline."

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Dear verginia,
Many thanks for joining in and for your kind comments. I really would imagine that Magnesium oil would be much safer than oral magnesium,-- but then I am not sure, being new to Magnesium myself, and starting out on an alarmist note-- which I hope is wrong, and which I hope will be proven wrong by the learned members here. Please go on following this thread and posting your experiences! Thank you again,

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Dear April1995,

Thank you for joining in and bringing your valuable experiences before us! Thank you also for thinking of me. You have raised a most important and pertinent point-- it was just what I had been apprehending. You had this slow and insidious urinary tract infection in the bladder -- and you had this swelling in the ankles etc. You went to a doctor and he ignored these symptoms as relating to the kidneys! And they were related to them!
If you had got a kidney function test at the time when you had the bladder infection I am sure the results would have shown a worsening kidney. They say that kidney function is measured by the creatinine which should remain between 0.5 - 1.5 which is a very narrow range. And if the creatinine is at 1.5 or is 1.6 or more then the kidney is in trouble.
I bet if you had measured the creatinine by a blood test at the time when you had the bladder infection it would have been high --even up to 2.0 or so.
This would have meant that the kidneys were not filtering out waste matter efficiently, which would then accumulate inside them -- making the kidney even worse!

What worries me about magnesium is the fact that the drug companies which sell the product themselves add this word of caution about the kidneys. Normally they would be expected to hide this aspect of it or minimize its dangers just to make money - but here they are warning people that Magnesium could be bad for the kidneys.

It is a well known fact that amongst many people the symptoms of a urinary tract infection are not evident. They call it "asymptomatic". But the kidney is still being affected.

Imagine our having osteoporosis for years before we come to know of it. Imagine a more dreadful scenario of having a deteriorating kidney -- either due to age or infection, or too much protein, or too many minerals or medicines. And on top of that if we take something like Magnesium -- without getting the kidney function tested -- then we are in for trouble!

I believe Ted has aptly said that we must not take Magnesium in Kidney Failure. However how does a common man know if he has a mild degree of kidney failure without symptoms? People do not routinely get their creatinine tested every time they take a mineral tablet.

If one has a mild degree of kidney failure my apprehension it that it can be made much worse by taking magnesium which will get "stuck" inside the kidney and thus send it into acute renal failure which is a nightmare situation!

Maybe taking normal foods with the normal amount of Magnesium might be the way Nature intended us to be. When we eat protein in normal foods it gets absorbed well --however when we start taking protein in fortified protein tonics we are frequently asking for trouble for the kidneys.

However -- as I said, my post may be somewhat alarmist, and I am waiting for greater clarification from those who have been taking magnesium and getting their kidney functions tested side by side.

Also it would be a great thing if stopping magnesium could cause the kidney to come back to normalcy, even if it was damaged by the element. The worst thing is "irreversible" damage.

Thanks for your very valuable experience, please continue to join in with any further observations.

Best wishes and warm regards,

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Dear honeybee,

Thanks for joining in. Please dont stop taking magnesium on the basis of this somewhat alarmist post. Please get your kidney function checked by a simple blood test of the value of Creatinine which should be between 0.5 -1.5. And if it is normal then go on taking whatever you have been taking. But if it is not, then please check with your doctor and ask him whether you should take the risk of taking magnesium or other minerals. I felt the same way as you do now and am hesitant to start magnesium until I get the kidneys tested first.
Best wishes,
Yours, Priya

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Dear millie,

Thank you so much. It was nice to hear from you again and to get your learned comments. Yes, you are right even a urine test would tell us something about the kidneys, though not as much as the blood test for creatinine which should be between 0.5 - 1.5 for a normal kidney. But your observation that low amounts would be safe is indeed a life-saver. So maybe I will start with 100 mg to 250 mg at the low dosage if I start magnesium. The dosages you mention are in milligrams.
Thanks do much for this valuable information!
Best wishes,

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Dear Ted,

We owe it to you to provide us with the best knowledge and information on any subject here, which equals that of any medical researcher in the field. I am going to log on to the sites you have mentioned. Thanks for once again underlining the importance of magnesium.

There is one topic of concern here: namely how are we as laymen to know that our kidneys are not normal, especially when there are no symptoms. Not everyone knows he or she has a urinary infection till it is in the late stage, and not all elderly folk know how their kidneys are functioning. The protein intake is reduced for the elderly for that reason, I think, so that the protein does not worsen the kidney.

While cases of overt kidney failure come to the notice of all -- with ankle swelling and facial swelling -- how does one know if one is in a state of mild kidney failure? And many would be without knowing it.

So if a person with mild kidney failure say with a creatinine close to 1.5 or more, were to take Magnesium what would happen to his kidneys? Would they take a downhill course and head for acute renal failure?

Also if we get kidney failure from magnesium, then would stopping the magnesium make the kidneys normal again -- or would the damage be irreversible?

Would you recommend that anyone starting Magnesium get his kidney function tested first -even if he has no overt symptoms of kidney failure?

This is the question that is worrying me. Most people who take vitamin and mineral pills are unaware of this kind of situation and just go on taking the pills without getting the kidney function tested at any stage.

If we take magnesium -- this would mean getting the kidney function tested before we start, getting the kidney function tested while we are taking it, and getting the kidney function tested after we have stopped it.

I shall greatly appreciate your giving us more information on this subject!
Thank you for your expert and excellent help and guidance always.

Best wishes,

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Dear animalmover,

Thanks for writing in. I can well understand your concerns with a kidney function being lower than normal. I dont know anything about massaging magnesium into the skin and its effects on the kidney function.

However I do know that there are certain pain killer creams which we massage into the skin where they tell us of the "systemic" effects of the cream, which means how the cream effects the internal organs.

Please check with your doctor and stop the magnesium if he so advises. The kidney is much too important an organ for us to take liberties with it for the sake of other benefits howsoever important.

If I were in your position, with a compromised kidney, I would not take magnesium in any form, but that may be just me!!

Best wishes and warm regards,

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Dear Deskjockey,

Thank you for writing in! Yes, you have very aptly described the situation! Food sources are the best in contrast to concentrated pills.However we have to be careful even with the foods we take when kidney function is compromised.

I recall there are special diets for people in various stages of kidney failure -- restricting food proteins being the first. And of course restricting tablets in any form or minimizing their dosage.

But why take anything that is harmful to the kidney in any case, whether food or tablets. I suppose the elderly are at the greatest risk since their kidney function is slow. Thanks for your valuable opinion!
Wishing you the best of health,

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