Ghost Fitness/Magnesium/What are the side effects of taking too much magnesium?
What are the side effects of taking too much magnesium?
The short answer
A ladder: surplus over about 400mg brings loose stools, then diarrhoea, nausea and cramping, self-limiting in healthy adults. True hypermagnesaemia, lethargy, low blood pressure, weakness and slowed heart, needs failed kidneys or laxative-scale intake, and comes from magnesium laxatives and antacids far more than capsules.
- Rung one: surplusloose stools, the osmotic effect; oxide worst, bisglycinate least
- Rung two: well overdiarrhoea, nausea, abdominal cramping; self-limiting, dose reduced
- Rung three: hypermagnesaemialethargy, low blood pressure, weakness, slowed heart: failed kidneys or grams from laxatives
- The sourcemagnesium laxatives and antacids, not supplement capsules, in nearly every serious case
Our brand: the worked example on this page
Futuro Labs Magnesium Glycinate
- 22p a day
- 180 capsules, 2 capsules daily
- Lab tested
- Made in the UK
The salt lowest on the ladder, at a dose under the level: Futuro Labs Magnesium Glycinate on Amazon UK, bisglycinate, 300mg elemental at 80% NRV, £19.99 for 90 days at 22p. Full label breakdown. The signs page is here; the removal page on the excess page.
The ladder, because the side effects of too much magnesium arrive in an order that depends on the dose and the kidneys
The side effects of taking too much magnesium arrive as a ladder, each rung needing more magnesium than the last, and reading them in order tells a reader which rung a given dose can reach. Rung one, a surplus over the UK supplemental guidance level of about 400mg a day in a healthy adult: loose stools, the osmotic effect of unabsorbed magnesium drawing water into the bowel, arriving within hours, scaling with the unabsorbed amount and therefore with the salt, oxide worst because least absorbed, citrate moderate, bisglycinate least, and being the reason most people never reach the second rung, the gut telling them to reduce the dose the same day. Rung two, well over the level, several hundred milligrams above it: frank diarrhoea, nausea, abdominal cramping, the same osmotic mechanism at volume, still self-limiting in a healthy adult because the excess leaves in the stool and the kidneys excrete what is absorbed, and still a matter of reducing the dose rather than of harm. Rung three, hypermagnesaemia, a raised blood magnesium: lethargy, nausea, flushing, low blood pressure, muscle weakness, loss of reflexes, slowed heart conduction and, at the extreme, respiratory depression and cardiac arrest, and this rung is not reached by a capsule habit in a healthy adult, because normal kidneys excrete surplus magnesium efficiently, so it needs one of two things, impaired kidney function, where excretion fails and an ordinary dose accumulates, or laxative-scale intake, grams of magnesium at a time from magnesium laxatives, Epsom salts or antacids taken in quantity, which is the source in nearly every serious case in the literature.
The source teach, why capsules rarely climb the ladder, and the side effects filed by rung
The source teach is the useful part of the page, because the worry attaches to capsules and the cases attach to something else: the hypermagnesaemia case reports are overwhelmingly people with kidney disease taking magnesium-containing antacids or laxatives, elderly patients on magnesium hydroxide for constipation with declining kidney function, and occasional massive ingestions of Epsom salts, the common thread being grams of highly available magnesium in a body that cannot excrete it, while a supplement capsule habit at 300mg of elemental magnesium, or even the 500mg the too-much page calls surplus, in a healthy adult produces rung one at most and never reaches rung three, the kidneys clearing what the gut absorbed. The variants asking about too much bisglycinate specifically have the gentlest version of the answer: bisglycinate is the salt best absorbed and least laxative, so it climbs rung one later than oxide or citrate and no faster to rung three, the ceiling being the same kidneys, and a bisglycinate reader's too much is a loose-stool morning that a smaller dose fixes. The side effects filed by rung: over the level, loose stools; well over, diarrhoea, nausea and cramping, self-limiting; and hypermagnesaemia's lethargy, low blood pressure, weakness and slowed heart only with failed kidneys or laxative-scale intake, the gates being kidney disease, where any magnesium needs a doctor, and the hidden magnesium in laxatives and antacids that the not-with page counts, with the worked example being the salt lowest on the ladder at a dose under the level, bisglycinate at 300mg elemental and 80% NRV, £19.99 for 90 days at 22p.
| The rung | The side effects | What reaches it |
|---|---|---|
| Surplus over ~400mg | Loose stools; osmotic | Any salt in surplus; oxide first, bisglycinate last |
| Well over the level | Diarrhoea, nausea, cramping; self-limiting | Several hundred milligrams over, in a healthy adult |
| Hypermagnesaemia | Lethargy, low blood pressure, weakness, slowed heart | Failed kidneys, or grams from laxatives and antacids |
| The extreme | Respiratory depression, cardiac arrest | Massive intake with impaired excretion; hospital |
| The source in serious cases | Magnesium laxatives, Epsom salts, antacids | Rarely, if ever, supplement capsules |
| The worked example | Rung one at most, late | The best-absorbed salt under the level |
The verdict, a ladder most people never climb past the first rung
What are the side effects of taking too much magnesium: a ladder, loose stools at a surplus over the 400mg level, then diarrhoea, nausea and cramping well over it, both osmotic and self-limiting in a healthy adult whose kidneys excrete the surplus, and hypermagnesaemia's lethargy, low blood pressure, weakness and slowed heart only with failed kidneys or laxative-scale intake, the serious cases coming from magnesium laxatives and antacids rather than capsules. The salt lowest on the ladder: Futuro Labs Magnesium Glycinate, bisglycinate, 300mg elemental at 80% NRV, £19.99 for 90 days at 22p a day, a rung-one salt at a dose that rarely reaches it.
What to check on the label
- Read the ladder in order: stools, then gut, then blood.
- Expect rung one from surplus: reduce the dose and it stops.
- Know what reaches rung three: failed kidneys or grams from laxatives.
- Count the hidden sources: laxatives and antacids, not capsules.
- Treat kidney disease as the gate: any magnesium needs a doctor.
Our brand
The worked example: Futuro Labs Magnesium Glycinate
Futuro Labs Magnesium Glycinate is the worked example for magnesium reviews because its label states every number a review needs: 1500mg magnesium bisglycinate at 20%, 300mg elemental, 80% NRV, 2 capsules a day, 180 capsules for £19.99, 22p a day, UK made, vegan HPMC shell, batch tested for lead, mercury, arsenic and cadmium, and only the register's own magnesium claims printed.
- Elemental magnesium per serving
- 300mg (80% NRV)
- Form
- magnesium bisglycinate 20%
- Serving
- 2 capsules a day
- Bottle
- 180 capsules, 90 days
- Price
- £19.99 (22p a day)
- Capsule
- vegetarian shell, vegan product
Questions people also ask
What happens if you take too much magnesium glycinate?
In a healthy adult, loose stools at a surplus over about 400mg elemental and diarrhoea, nausea and cramping well above it, both osmotic and self-limiting, bisglycinate reaching these later than oxide or citrate; hypermagnesaemia needs failed kidneys or laxative-scale intake.
Can magnesium supplements cause hypermagnesaemia?
Rarely: normal kidneys excrete surplus efficiently, and the serious cases in the literature involve kidney disease or grams of magnesium from laxatives, Epsom salts and antacids, not capsule habits at a few hundred milligrams.
What are the symptoms of dangerously high magnesium?
Lethargy, nausea, flushing, low blood pressure, muscle weakness, loss of reflexes and slowed heart conduction, progressing at the extreme to respiratory depression and cardiac arrest, a hospital emergency treated with intravenous calcium and, where needed, dialysis.
Is diarrhoea from magnesium dangerous?
No: it is the osmotic effect of unabsorbed magnesium and the body's own dose limit, stopping when the dose is reduced, with prolonged diarrhoea from any cause worth a GP's attention for fluid loss.
Who is at real risk of taking too much magnesium?
People with impaired kidney function taking any magnesium, including antacids and laxatives, and anyone ingesting grams of magnesium at once from laxative products, rather than healthy adults taking a labelled supplement dose.
Sources
- The hypermagnesaemia literature: raised serum magnesium is rare with normal kidney function and occurs with impaired excretion or massive intake from magnesium laxatives and antacids, presenting with nausea, lethargy, low blood pressure, muscle weakness and slowed heart conduction, and treated in hospital with intravenous calcium and, where needed, dialysis. PubMed record
- Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals. Food Standards Agency, 2003 (magnesium guidance level 400mg a day from supplements). https://cot.food.gov.uk/sites/default/files/vitmin2003.pdf
- The hypermagnesaemia literature: the kidneys excrete surplus magnesium, so supplementation is safe for healthy adults within guidance and warrants medical advice in chronic kidney disease, where impaired excretion allows magnesium to accumulate. PubMed record
- Firoz M, Graber M. Bioavailability of US commercial magnesium preparations. Magnesium Research 2001;14(4):257-262. PubMed record