Magnesium blood test: normal range, low and high results, and price

A magnesium blood test measures the magnesium in the liquid part of your blood (serum). It shows whether the level is low or high, and it often helps explain a low potassium or a low calcium. What it does less well is show how much magnesium the body holds overall, because the blood carries a tiny share of it.

What it measures

The body needs magnesium for muscles, nerves and the heart to work properly, to help control blood pressure and blood sugar, and to build bone. About half of the body's magnesium is in bone and most of the rest is inside cells; serum holds about 0.3% of it.

Within serum, between 55% and 70% of magnesium is free (ionised), the active form, about 30% is bound to proteins, mainly albumin, and the rest is attached to other small molecules. The body draws on the magnesium in bone to keep the blood level steady, so a normal blood result can sit alongside low stores.

Normal range

Result	mmol/L	mg/dL
Typical adult reference range	0.70 to 0.91	1.7 to 2.2
Common definition of low magnesium (hypomagnesaemia)	below 0.65	below 1.5

Ranges vary by laboratory, method, age and sex, so read your result against the range on your own report. The lower limit is also debated. The commonly quoted interval of 0.75 to 0.95 mmol/L was set from US population data gathered in 1974, describing what was typical rather than what was healthy, and the authors of a 2016 review proposed 0.85 mmol/L as the lower limit for adequate magnesium. A result near the bottom of the range is therefore worth reading in context.

What a low magnesium usually points to

• Losses from the gut, from long-lasting diarrhoea or conditions that reduce absorption, such as Crohn's disease or ulcerative colitis.
• Losses through the kidneys, including in poorly controlled diabetes and kidney disease.
• Medicines. Proton pump inhibitors, the acid-reducing medicines, are linked with low magnesium: a pooled analysis of 16 studies found about 1.7 times the odds. Thiazide and loop diuretics, some antibiotics and antifungals, calcineurin inhibitors used after transplants, and cisplatin are also linked.
• Alcohol use disorder and low intake from food.
• Pancreatitis, high calcium, and, in pregnancy, pre-eclampsia.

Low magnesium rarely travels alone. It makes the kidneys lose potassium, and it blunts the release of parathyroid hormone, which can bring calcium down. So a doctor who finds a low magnesium will typically look at potassium and calcium too, and magnesium is one of the tests used to find the cause of an abnormal potassium or calcium. Next steps can include kidney function, a review of medicines, and sometimes a urine magnesium or red blood cell magnesium test.

What a high magnesium usually points to

High magnesium is rarely caused by food alone. It usually follows too much magnesium from supplements, laxatives, antacids or some prescription medicines, and kidney failure, which stops the excess being cleared, is the most common medical cause. Dehydration, diabetic ketoacidosis, adrenal insufficiency, lithium and milk-alkali syndrome are also listed. A doctor will typically check kidney function through creatinine and eGFR, and ask about every product containing magnesium.

What moves magnesium

• Haemolysis. Red cells breaking open in the tube push measured magnesium up.
• EDTA contamination. Carry-over of this anticoagulant from another tube can make magnesium read falsely low. One hospital laboratory study found EDTA in 4.8% of samples with a magnesium below 0.7 mmol/L.
• Low albumin, which can make serum magnesium read low.
• Supplements and medicines. Magnesium-containing supplements, laxatives and antacids raise it; diuretics and proton pump inhibitors lower it.
• Pregnancy, which can lower it.

Preparing for the test

There is usually no preparation for a magnesium test. You may be asked to fast for several hours if other tests share the sample. Tell the person taking the sample about all medicines and supplements, including magnesium tablets, laxatives and antacids. Whether any of them should be paused is for your doctor to decide.

How Clare's panel handles it

In Clare's panel, magnesium is measured by the lab, on the same sample as calcium, potassium and phosphorus, so the minerals it interacts with can be read together. When Clare opens, your magnesium will sit beside your earlier results, with plain explanations in English and Arabic.

Why it matters in the UAE

Diabetes is common in the UAE: the International Diabetes Federation puts prevalence among adults at 20.7% in 2024. Low magnesium is linked with diabetes, and there is Gulf data on the link. In the Qatar Biobank study of 9,693 Qatari adults, 59.5% had a serum magnesium below 0.85 mmol/L, and diabetes was 2.7 times as common in the quarter with the lowest magnesium as in the quarter with the highest. That is an association, not proof that one causes the other, but it is a reason to read magnesium beside HbA1c and fasting glucose. HbA1c, glucose and insulin: reading them together explains those markers.

Price in the UAE

Magnesium is not part of every kidney function test, and several of the packages we read do not list it, so it is usually bought within or alongside one. When we read public prices on 11 October 2026, a kidney function test cost from 89 to 900 at 6 UAE providers. VAT is rarely stated, some are offer prices or starting prices, and home collection can add a fee. Check that magnesium is on the list before buying.

Related tests

Magnesium is read with calcium and potassium, both of which it affects, and with phosphorus, since magnesium plays a part in how the body absorbs all three. Creatinine and eGFR show whether the kidneys can clear it.

Why the number means more over time

Because the body defends its blood magnesium by drawing on bone, one normal result can sit alongside a slow decline in stores, and one low result may reflect a recent bout of illness. A series of results taken the same way shows which way the level is heading. That is useful for people taking a medicine linked with low magnesium, such as a long-term acid reducer or a diuretic, and for people living with diabetes. If your magnesium sits low or is falling across tests, talk to a doctor about it with the results in front of you. Clare is opening with a waitlist at clare.health.