Elderly patients (increasing by the day as “baby boomers” turn 65) are at risk from magnesium deficiency, most commonly when they are taking diuretics, proton pump inhibitors, or both simultaneously. If you need help with your estate planning, you can check it out here! 
Magnesium deficiencies can also occur in the diet because many pasture soils are deficient in magnesium.
(See Overcoming Magnesium Deficiency
http://www.bioag.com.au/products-programs/solid-nutrients/magphos/overcoming-magnesium-deficiency/)

“Pasture soils in many parts of Victoria and NSW suffer from magnesium deficiency, raising risk of incidence of grass tetany in beef and dairy herds. Grass tetany can result from a number of causes, but a common reason is a lack of magnesium”

“Rainfall, pasture species, grazing management and nutritional fertility all influence the ability of a pasture-based enterprise to reach its full potential. The nutrients calcium, potassium, nitrogen and phosphorus each have an impact on the potential pasture yield; however, in some cases where adequate levels of these elements are present, a magnesium deficiency can prevent a pasture from achieving its maximum yield.”

A report has just been released in Medscape (http://www.medscape.com/viewarticle/832574 ) that was originally published online in Plos Medicine (30 September 2014) relating to elderly patients that had been hospitalised in Ontario, Canada, with low levels of magnesium. The Medscape report stated:
“Elderly patients taking proton-pump inhibitors (PPIs) were at a 43% increased risk of being hospitalized with hypomagnesemia, according to a population-based case control study. The risk was concentrated among patients taking both a PPI and a diuretic”.

“When the investigators stratified patients according to diuretic use, they found that those patients receiving both a PPI and a diuretic had a 73% increased risk for hospitalization (95% CI, 1.11 – 2.70) compared with those receiving neither drug. In contrast, the risk among those taking a PPI but no diuretic was no longer statistically significant (adjusted odds ratio, 1.25; 95% CI, 0.81 – 1.91)”

Obviously the patients identified in the above study would have benefited from a magnesium supplement which may have also alleviated accompanying symptoms of magnesium deficiency such as muscle cramp, cardiac arrhythmia or hormone imbalances.
Or alternatively suggested by one Medscape commentator on the study:

“Patients prescribed diuretics are already losing magnesium, and PPIs “could tip the balance,” she said. Clinicians should strongly consider discontinuing PPIs for these patients. In addition, physicians need to do a better job, in general, of evaluating the need for PPIs in patients whose symptoms have resolved. “There are a lot of people who get on these [medications] and stay on them,”

In the past I spent some time as a hospital pharmacist and it was always a worry for me that when patients came in to the intensive care ward, one of the first treatments given for cardiac problems was IV magnesium sulphate.
On discharge, the same patient was prescribed an assortment of drugs but no ongoing supplement of magnesium. This continued to be the case despite persistent interventions suggesting the patient be discharged with a magnesium supplement.

The body has a homeostatic mechanism for maintaining adequate levels of magnesium with any supplementation surplus to requirements being simply blocked for absorption.

Patients prescribed a diuretic will commonly be prescribed a potassium supplement to replace the loss incurred by the diuretic. But magnesium never seems to be considered, yet excretion and loss is similar to potassium.

Magnesium levels in the body are hard to measure as blood levels are not necessarily reflective of tissue levels, which can be quite low.
Magnesium is utilised from bone stores when a deficiency is present, so osteoporotic patients can also be put at risk if prescribed PPI + diuretic combinations.
Not only are magnesium levels affected, but calcium levels as well.

Given that PPI’s are readily available over-the-counter at most pharmacies, it is obvious that the question to be asked of any patient purchase is “Are you taking any prescribed medications that may contain diuretics?”

It is not so long ago that the PGA and Blackmores developed a marketing strategy where nutritional supplements were to be recommended by pharmacists automatically in the instance that they were taking PPI’s and diuretics or both.
The process was ridiculed and mocked as a fast food approach “Will you have coke and fries with that?”

In this particular instance it seems that patients may have generally benefited because they would have been definitely magnesium deficient and a blood test may not have revealed that.
The best approach would have been for a pharmacist to offer a magnesium supplement (quite safely because of homeostasis), provided there was an inquiry as to the patient’s renal status and a referral to the GP with a suggestion to drop/replace the PPI’s.

At the time of the uproar between medical Skeptics, the PGA and Blackmores, i2P commented that the PGA was on the right track but went about it the wrong way with the “naysayers” getting in an opportunistic plug for their view of the world.

That attitude does deter health practitioners from using complementary medicines, but there is a definite place for them. And it will not stop them being used by health practitioners and self-care patients.
In the above example, not proceeding with the above marketing program would have allowed for considerable patient damage.
Interestingly, those most vocal in the negative seem to have had little training or indeed have a practice involving interaction with patients