One Out, One In #1: magnesium oxide → glycinate

One you drop. One you take instead.

3. Oxide is a poorly absorbed salt. Fat number on the label. Loose in the bowel.

2. Leave the “high strength, three forms” bottle if most of the elemental magnesium is still oxide.

1. Named soluble form. Glycinate for everyday. Citrate if the toilet is the goal. Read elemental milligrams.

The cheap tub is magnesium oxide. It is about 60% elemental by weight, which is why the label looks generous. A US tablet marked “magnesium oxide 400 mg” is 241.2 mg of actual magnesium.

In Australia the oxide is often hidden. Nature’s Own High Strength Magnesium prints 350 mg elemental and talks about “three forms including easily absorbed magnesium citrate.” One tablet is 515.46 mg oxide = 300 mg elemental, plus 25 mg from a chelate and 25 mg from citrate. That is 86% oxide sold on a sprinkle.

Forms that dissolve well are absorbed more completely than oxide. NIH ODS names aspartate, citrate, lactate and chloride — not glycinate — as beating oxide and sulfate in small studies. Unabsorbed magnesium salt stays in the gut, pulls water, and you get diarrhoea. ODS lists oxide among the forms most commonly reported to cause it.

That is not the same thing as a hospital laxative. Milk of Magnesia is hydroxide. The US saline-laxative actives are citrate, hydroxide and sulfate. Oxide’s own US label is an antacid that “may have a laxative effect.” If the cheap tub “worked” because you got the runs, that was osmosis, not magnesium status.

Opposite trap, same aisle: Blackmores MagMin “500 mg” is 500 mg aspartate, which is only 37.4 mg elemental. Nine tablets a day for women, eleven for men, on the brand’s own directions. Huge front, tiny magnesium.

Park oxide if the goal was sleep, cramps, or “I heard magnesium is good.” Keep it only if a clinician put you on it.

If the goal is magnesium, pick a named soluble form and read the elemental line.

Glycinate (also labelled bisglycinate — same chelate) is the everyday, gut-gentler option. Honest labels sit around 13–14% elemental (Blackmores 1.1 g glycinate = 150 mg elemental; Nature’s Own 1150 mg = 150 mg). Stay at or under 350 mg supplemental elemental unless a clinician is running something else. Food magnesium does not count toward that cap. Adult food-plus-pills targets are about 310–320 mg for women, 400–420 mg for men.

Citrate if constipation was the actual point. Do not pretend glycinate is a laxative. A labelled saline laxative (hydroxide / Milk of Magnesia) is the other honest toilet product — ask a pharmacist if that is really the job.

There is no healthy-adult trial proving glycinate absorbs better than citrate. Walker’s “amino-acid chelate” is not glycinate, and citrate beat it on serum magnesium. Do not fight about brands. Fight about oxide vs a named soluble salt.

Glycinate is not a sleeping pill. One 2025 trial of 250 mg elemental bisglycinate in 155 adults who already slept badly found a small drop in insomnia scores (Cohen’s d = 0.2, p = 0.049). No effect on stress, mood, or anxiety. Cochrane: magnesium is unlikely to help night cramps in older adults. Buy glycinate because the form is named and the gut is kinder. Do not buy it as Ambien, and do not buy it because the bottle says “relieves cramps.”

Skip the 12-in-1 night mix. Scan magnesium bottles for vitamin B6 — some AU mags add it; tingling or numbness is a GP visit, not a bigger tub. An AUST L number means the ingredients were allowed, not that TGA tested this bottle for absorption or sleep.

“I’m taking magnesium oxide. If the goal is magnesium status rather than a laxative, is a more soluble named form such as citrate or glycinate reasonable for me, given my kidneys and other medicines — especially bisphosphonates, antibiotics, diuretics or a PPI?”

If the toilet was the point:

“I’ve been using magnesium oxide. If the aim is constipation, would magnesium citrate or another saline laxative be more appropriate for me, given my kidneys?”

This is information, not a prescription. Keep / park / ask your GP. One In publishes this letter. We do not sell the bottles. If a clinician already has you on something, they win.