How to Test Your Magnesium Levels: 6 Ways

how to test magnesium levels

Your body needs to maintain a healthy level of vitamins and minerals to produce a healthy body and a healthy lifestyle. Being deficient or over-abundant in mineral levels can lead to dysfunctioning organs and even organ failure. One of the most important minerals in the body is magnesium. It helps your body maintain energy levels, blood sugar, blood pressure and keeps your heart, bones, muscles, and nerves in good healthy condition.

Your doctor may order a magnesium test if you show signs of high or low magnesium levels or if you have diabetes or kidney trouble. Magnesium is found inside bones, muscles, and brain tissue. Its location makes it difficult to accurately assess the amount of magnesium in a patient’s body. Regardless, testing methods have been developed to estimate magnesium levels.

Here are the 6 known methods for measuring magnesium levels in the body:

1. Blood test

The most common and least accurate magnesium test is the blood serum test. It is chosen often due to the ease of access and turnaround time for healthcare providers. The process requires a blood sample to be taken from the patient and delivered to the lab to separate and measure.

All the patient experiences is a nurse cleaning a draw point on their arm, a small prick, and then clean up and bandaging. After the results have been gathered, the doctor will estimate the magnesium levels based on the levels found in the blood. This method is highly inaccurate because blood only contains 1% of the total magnesium in a human body.

magnesium blood test

It is recommended to avoid using the blood serum test to determine magnesium levels in the body as the inaccuracy has a high potential to cause misdiagnosis and thus mistreatment.

The blood serum test is well suited and efficient for many purposes but not for measuring magnesium.

2. RBC Test

A more accurate test also utilizing blood is the red blood cell biopsy or RBC test.

The patient experiences the exact blood sample process as a blood test and may even have had multiple samples taken to run different labs. The difference lies in the lab process.

A red blood cell test differs from the blood serum test in only one manner. Instead of testing the serum for magnesium, this test looks into the red blood cells themselves. It is considered to be more accurate but reserved for kidney disorders or diseases due to the longer turnaround time of two to four days. However, the higher accuracy of this test makes it a much better option to test magnesium levels. As much as we may want to gain results as soon as possible, in some situations the fast options can lead to costly mistakes.

3. Ionized Magnesium Test

Claimed to be the most accurate blood test, also the rarest, is the ionized magnesium test.

Utilizing specialized blood analyzing machines, lab doctors can isolate the magnesium ions found in the body for the most accurate measurement that can be done with a blood sample.

The validity of the accuracy of the ionized magnesium test has been put into question as new studies show that the total serum magnesium measurements did not correlate with ionized magnesium measurements in 30% of ICU patients. This does not discount the use of the test entirely but may suggest it needs improvement to the methods in order to provide a more accurate measurement.

Ionized magnesium tests are more widely than before but they are still far and few in between. Reliably finding a lab with the capability to perform the test is difficult. It may also be that ionized magnesium measurements are not being used as a measurement method of magnesium levels in the body. While most doctors won’t have the option to request this test, they may not want to until it can be honed in.

4. EXA Test

EXA Test, Energy Dispersive X-Ray Analysis, is a reliable noninvasive method.

This test utilizes tissue samples scraped from the mouth. Cells from the sample are prepared on slides to be sent to a diagnostics team. The slides are then viewed by an analytical scanning electron microscope. EXA uses a proprietary analysis method to light up the slides with electrons and measure the wavelengths of the released energy to measure unique signatures that identify each mineral element.

exa magnesium test

After spectral image information is gathered, they run data analysis software to calculate a map for each patient that identifies mineral electrolyte levels and ratios from the sample. The results are then delivered to the health care professional with an advisory risk factor for each mineral. These results can then be used to evaluate a patient’s intracellular mineral electrolyte status.

The testing of soft tissue should provide a higher accuracy level of the magnesium in a patient’s body versus a blood sample. The EXA test, unfortunately, is also not widely available and it may be difficult to find a lab that can perform the test. If this option is available, it is the current best method for accuracy in measuring magnesium levels in a body. It is also rather expensive.

5. Urine Test

A somewhat more interactive test for patients is the urine sample test.

This test requires the patient to collect urine samples during a 24-hour period to be measured for magnesium waste products. This test is aimed at more specific diagnostic purposes as it will measure magnesium waste deposit levels through a day but not the total magnesium in the body. A urine test will normally be ordered to narrow down kidney problems.

The urine test has a three-day turnaround time due to the 24 hour collection time and amount of samples to be analyzed. However, the heavy patient involvement also means this test can be prepared at home and sent to the lab.

While it may be thought to be a more convenient method of testing, the ‘do-it-yourself’ aspect can draw attention from individuals seeking to avoid a visit to the doctor’s office and can potentially lead to patients misdiagnosing their ailments. It is important to note that while these tests will produce results, the evaluation of the results is best left to medical professionals with the ability to determine the meaning behind the results.

The inexpensive nature of this method lends itself to general practitioners lending a hand to patients with inadequate or no insurance. Diagnostics can be an expensive endeavor but the necessity of understanding a patient’s ailments is important. When solutions that can help solve problems and relieve financial stress are available, they should be utilized.

6. Magnesium Loading Test

The last available option is the magnesium loading test.

This is another urine sample test but with a fun twist. The doctor injects the patient with a safe sizeable amount of magnesium and then asks the patient to collect samples or to return the next two days consecutively to collect samples himself/herself. It should be noted for patients transporting urine samples that it might be wise to place the sample containers in a small plastic lidded bin together and to take proper care when carrying the samples from the car to the hospital or general practitioner’s office.

The amount of magnesium deposit in the urine can be used to determine how much magnesium a patient’s kidney is absorbing. If the levels of magnesium in the urine are low, it is assumed the body had a deficiency. If the levels of magnesium in the urine are high, either the body was sufficient in magnesium or the kidney is having trouble absorbing it. Either way, a significant amount of functional information is gathered that can help to remove possibilities from the list.

This test is practical and inexpensive. While it is not the most informational method, it is an acute diagnostic solution that can be used in between the turnaround time for lab results. It also provides more doctor-patient interaction that can be used to further improve diagnostic options and results. It can also give the patient a feeling of involvement and control in their healthcare.


Each method for measuring magnesium levels offers a slightly different result. The most accurate method for determining the actual level of magnesium in a patient’s body seems to be the EXA test. However, access to EXA test-capable labs is limited and diagnostic solutions need to be reliably accessible and relatively quick. This makes the red blood cell test a more viable solution as an accurate method that can be consistently performed. It may be prudent to perform a loading test as well to gather more information on the current performance of the patient’s kidney. The more information about the status of the patient, the more accurate the diagnosis can be.

While there are only six methods, using the types of results provided by the test is a good way to choose which method will ultimately best serve the intended purpose.