Managing hypomagnesemia: A complete guide to nursing assessment and treatment of low magnesium levels
Published: March 26, 2023
Last Updated: April 10, 2023
Hypomagnesemia, the medical term for low magnesium levels in the blood, can have disastrous consequences if left untreated. Magnesium is crucial in numerous bodily functions, including nerve and muscle function, heart rhythm, and bone health. Hypomagnesemia can lead to serious complications, such as seizures, cardiac arrhythmias, and even death.
As a nurse, knowing the causes, symptoms, and treatment of hypomagnesemia is essential to provide effective care and improving patient outcomes. This article will provide a comprehensive guide to nursing assessment and treatment of hypomagnesemia, including its causes, clinical manifestations, nursing assessment, treatment, and monitoring.
Why is Magnesium So Important in the Body?
Magnesium is an electrolyte that is so important for our body’s daily functioning. Magnesium is essential from the cardiovascular system to our muscular system and energy metabolism! When low magnesium levels occur, this can cause issues in these areas! Magnesium functions in the following ways:
Magnesium acts similarly to a calcium channel blocker, helping to regulate the influx of calcium to control the proper timing and duration of electrical impulses in the heart. It also plays a crucial role in stabilizing the cell membrane and maintaining the resting membrane potential. Hypomagnesemia and low magnesium levels can lead to deadly cardiac arrhythmias.
Magnesium is important in the contraction of muscles as well as their relaxation. This helps with the funcitoning of cardiac muscle tissue, the GI system, and skeletal muscle tissue. It also relaxes the smooth muscle in the vessel walls, reducing blood pressure and preventing spasms.
Magnesium is necessary for metabolism as it is a co-factor for many enzymes involved in producing ATP – the body’s primary energy source on a cellular level. It’s also involved in the regulation of glucose metabolism and insulin signaling.
Magnesium is involved in transmitting nerve impulses and coordinating muscle movements, as it helps regulate the release of neurotransmitters and the activation of ion channels.
Magnesium supports the structural integrity of bones and teeth. It is also a co-factor for enzymes that regulate bone metabolism, and low magnesium levels are associated with osteoporosis.
How is Magnesium Regulated in the Body?
Magnesium, like potassium, is tightly regulated to maintain proper body function and prevent hypomagnesemia and low magnesium levels from occurring. The regulation of magnesium involves a complex interplay of factors, including dietary intake, absorption, excretion, and hormonal mechanisms.
Intake & Absorption
The body regulates its magnesium levels by adjusting how much magnesium it absorbs in the small intestine. When there are low magnesium levels, the absorption increases to prevent hypomagnesemia. The opposite is true as well!
The kidneys play a crucial role in regulating the excretion of magnesium, similar to its role in potassium.
Several hormones can influence magnesium levels. These include the Parathyroid hormone (PTH), which increases GI absorption and decreases kidney excretion. Vitamin D also stimulates magnesium absorption in the small intestines and regulates the activity of PTH.
Similar to hypokalemia, acid-base balance can also influence magnesium levels. Acidosis can cause magnesium to shift out of cells into the bloodstream and extracellular space. Alkalosis causes the opposite, leading to hypomagnesemia.
Normal Magnesium Levels & Hypomagnesemia
Normal magnesium levels can range from 1.7 to 2.2 mg/dL. However, only about 1% of the body’s magnesium levels are in the blood. 50-60% of magnesium is stored in the bone, and the rest is located in the muscles, soft tissues, and red blood cells.
Normal Levels: 1.9 – 2.2 mg/dL
Mild Hypomagnesemia: 1.6 – 1.9 mg/dL
Moderate Hypomagnesemia: 1 – 1.5 mg/dL
Severe Hypomagnesemia: <1 mg/dL
Causes Of Hypomagnesemia:
Several factors can contribute to hypomagnesemia, including inadequate dietary intake, malabsorption, renal losses, medications, and certain medical conditions. Understanding the underlying causes of low magnesium levels is essential for appropriate treatment and preventing long-term complications for our patients.
Hypomagnesemia can occur with excessive vomiting or diarrhea but occurs more often with diarrhea (it has 15x more magnesium in stool than in vomit).
Certain GI conditions that affect magnesium absorption include irritable bowel disease (IBD – AKA Crohn’s or ulcerative colitis), celiac disease, and pancreatitis.
Medications that increase magnesium loss from the GI system include chronic proton pump inhibitors (PPIs) like Omeprazole may lead to low magnesium levels. Other medications which can do this include H2 blockers, Antacids, and even laxatives.
Conditions that can lead to excessive kidney magnesium loss include renal tubular acidosis, hyperaldosteronism, and even diabetes. Certain medications can also impact this (discussed below).
Medications that can increase the excretion of magnesium in the kidneys include loop diuretics and thiazide diuretics. Other drugs that can cause hypomagnesemia include Aminoglycoside antibiotics, certain chemotherapies, calcineurin inhibitors, and Digoxin.
Chronic alcoholism can impair magnesium absorption in the small intestine and increase excretion in the urine, leading to hypomagnesemia. This magnesium wasting in the urine is reversible after four weeks of sobriety.
Patient’s with an organ transplant are more likely to experience hypomagnesemia, likely from their calcineurin inhibitor medications (like tacrolimus).
High calcium levels can lead to mildly low magnesium levels.
Certain rare genetic conditions can cause decreased magnesium absorption in the small intestine and increased renal magnesium wasting.
Nursing Assessment Of Hypomagnesemia
Symptoms of hypomagnesemia (low magnesium levels) will depend on the patient and the severity of their hypomagnesemia. As the magnesium levels drop, the symptoms become more pronounced, severe, and potentially life-threatening.
Like low potassium, muscle weakness is common with hypomagnesemia. They may experience fatigue and muscle weakness in their legs which can cause difficulty walking, as well as weakness of any other muscles in their body.
Muscle Cramps & Twitching
Patients may feel tingling sensations and experience involuntary muscle contractions, particularly in their hands or lower extremities.
As discussed above, magnesium is essential in the conduction as well as the mechanical beating of the heart. If an arrhythmia occurs, patients may experience palpitations, chest pain, shortness of breath, dizziness, or even syncope. Cardiac arrest is possible if they go into a deadly rhythm like VFIB.
Low magnesium levels can cause nausea, vomiting, or abdominal cramping. Additionally, if the patient has diarrhea, that may be a clue on the cause.
Magnesium can cause CNS hyperirritability, leading to confusion, irritability, hyperactive deep tendon reflexes, paresthesias, and seizures.
The physical assessment of a patient with hypomagnesemia will also depend on the severity of the low magnesium levels and other factors.
- HR: May be fast or slow, depending on any arrhythmias.
- BP: May be increased
- Respirations: usually normal
- SPO2: Usually normal
- Temp: Normal
- Muscle weakness or trouble walking or moving
- May appear fatigued or lethargic
- Auscultate for an Irregular heartbeat
- May have tender muscles
- Edema or ascites may indicate underlying kidney or liver failure
- Abdominal tenderness may be present, especially with any GI symptoms
Overall, while the nursing assessment of hypomagnesemia may not reveal many specific physical findings, monitoring for muscle weakness, irregular heart rhythms, and signs of potential underlying issues such as edema, ascites, and abdominal tenderness is important for identifying the condition and providing appropriate interventions to manage hypomagnesemia and prevent complications.
Treatment for Hypomagnesemia
The treatment for hypomagnesemia depends on the underlying cause, severity, and serum magnesium levels.
When you get your patient’s results back, and they show hypomagnesemia, then follow the following general interventions:
Assess the Patient
Ensure they don’t have any symptoms and are stable, including recent vital signs.
Make sure your patient is on the cardiac monitor. Obtain an ECG if it still needs to be done. Close cardiac monitoring is essential when infusing electrolytes through the IV as well.
Notify the Provider
Notify the provider of the potassium levels, your assessment, and their cardiac rhythm. They will order the treatment for hypomagnesemia!
Ensure IV access
Make sure there is at least one IV site, but place a second line if the hypomagnesemia is severe.
Evaluate if they are on any medications which may lead to hypomagnesemia listed above.
Administer medications that are ordered (discussed below).
Treatment for Hypomagnesemia (medications):
Treatment for hypomagnesemia will depend on the severity, as well as any symptoms the patient is having. Severe symptoms that require immediate and likely IV repletion include tetany, arrhythmias, or seizures.
Address Underlying Causes
Figuring out why the magnesium is low is essential, but there shouldn’t be any reason to delay replacing the magnesium with Oral or IV options. However, addressing the underlying cause can prevent further loss of magnesium and prevent it from happening again.
Oral Magnesium Supplementation
PO magnesium is the standard for mild to moderate hypomagnesemia, primarily if there are no or minimal symptoms.
There are many different variations of magnesium pills, such as:
- Magnesium Oxide: Most common and inexpensive, but it has a low absorption rate and may cause diarrhea.
- Magnesium Chloride: Has better absorption and higher bioavailability than magnesium oxide. Also less likely to cause GI side effects and may be better for skin health and wound healing.
- Magnesium Carbonate: Good for heartburn, but not the best absorption.
- Magnesium L-lactate: Less likely to cause GI symptoms like diarrhea.
- Magnesium Glycinate: Highly absorbable and less likely to cause diarrhea. It may have a calming effect on the body.
- Magnesium Citrate: Good absorption rate but also a laxative and will cause diarrhea and cramping. They are not typically used for magnesium replacement.
Generally, sustained release options are better because they minimize the renal wasting of the magnesium. Common options include:
- Magnesium Chloride 64-71.5mg elemental magnesium, 6-8 tabs in divided doses
- Magnesium L-lactate with 84mg elemental magnesium, 6-8 tabs in divided doses
If the sustained release is unavailable, magnesium oxide 800-1600mg daily in divided doses may be used, but diarrhea may occur.
IV Magnesium Sulfate
IV magnesium is given to patients with severe symptoms or who are NPO for whatever reason.
IV replacement dosing will depend on the severity:
- Mild (1.6 – 1.9 mEq/L): 1-2 grams of mag sulfate over 1 – 2 hours
- Moderate (1.0 – 1.5 mEq/L): 2 – 4 grams of mag sulfate over 4 – 12 hours
- Severe (< 1.0 mEq/L): 4 – 8 grams of mag sulfate over 12 – 24 hours
Patients in renal failure should be cautiously replaced with electrolytes like magnesium and potassium, as their ability to excrete those electrolytes is impaired. Therefore, dosing should generally be cut in half, and levels should be closely monitored.
Patients should generally be maintained on magnesium replacement for 1-2 days after the levels have normalized to replete intracellular magnesium. However, if ongoing losses occur, chronic therapy may be needed.
Monitoring of Hypomagnesemia
Monitoring patients with hypomagnesemia involves cardiac monitoring and trending the magnesium levels.
Magnesium levels are generally checked at least daily while inpatient until normalization of the magnesium level.
Other electrolytes and monitoring of renal function should also be checked, usually daily, every morning.
Patients with low magnesium are at high risk for cardiac arrhythmias. Additionally, anybody receiving IV replacement with magnesium should be on a cardiac monitor.
Foods High in Magnesium
- Seeds & Nuts (Pumpkin seeds, chia seeds, almonds, Cashews, peanuts)
- Dark Chocoloate
- Black Beans
Hypomagnesemia and Cardiac Arrhythmias
Magnesium is an important electrolyte that plays a crucial role in cardiac function, particularly in maintaining normal cardiac rhythm. Hypomagnesemia and low magnesium levels can lead to various cardiac arrhythmias, including:
- Torsades de Pointes: Torsades de Pointes is a type of ventricular tachycardia characterized by twisting the QRS complex around the isoelectric line. It can occur in patients with hypomagnesemia and prolongation of the QT interval and is classic with hypomagnesemia.
- Atrial fibrillation: Hypomagnesemia can increase the risk of atrial fibrillation due to magnesium’s effect on atrial muscle cells.
- PVCs: Low magnesium leads to impaired ion channels, leading to excitable cardiac conduction, which can trigger PVCs or VTACH.
On ECG, hypomagnesemia can manifest in the following ways:
- Prolonged QT interval: Hypomagnesemia can prolong the QT interval, leading to an increased risk of Torsades de Pointes.
- Widened QRS complex: Hypomagnesemia can cause a widened QRS complex, which can be seen on ECG.
- ST segment and T wave changes: Hypomagnesemia can cause ST segment depression and flattening or inversion of T waves on ECG.
It is important to note that hypomagnesemia can also exacerbate cardiac arrhythmias caused by other electrolyte imbalances, such as hypokalemia and hypocalcemia.
Nurses should be aware of the potential cardiac complications associated with hypomagnesemia and monitor patients for signs and symptoms of arrhythmias. Timely recognition and treatment of hypomagnesemia can help prevent severe cardiac complications.
Hypomagnesemia is associated with Torsades de Pointes, which is a type of polymorphic ventricular tachycardia that is deadly and will quickly degenerate into Ventricular fibrillation if not treated ASAP. Treatment involves following ACLS protocol, but often IV magnesium is given rapidly if hypomagnesemia is suspected as a cause.
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Hypomagnesemia is a condition that nurses should be familiar with, as it can have significant implications for patient health. Magnesium is vital in various bodily functions, including the cardiac, nervous, and gastrointestinal systems.
The body regulates it through dietary intake, absorption, excretion, and hormonal factors. Various factors, such as chronic diarrhea, alcoholism, and certain medications, can cause hypomagnesemia. Treatment often involves magnesium replacement, either orally or intravenously, and addressing any underlying conditions that may contribute to the deficiency.
Nurses are essential in identifying and monitoring hypomagnesemia and low magnesium levels and educating patients on the importance of adequate magnesium intake and potential risk factors. Nurses can provide optimal care and improve patient outcomes by understanding hypomagnesemia’s causes, symptoms, and treatment.
Also check out:
- Nursing Interventions for Hypokalemia: A Comprehensive Guide for Nurses
Treatment for Hyperkalemia: A nurse’s comprehensive guide to high potassium levels
- How to Read an EKG Rhythm Strip
- Intravenous Fluids: Types of IV Fluids
- The Ultimate ABGs Blood Gas Guide you Need to Calm Your Nerves
UpToDate & Other Database Sources:
- Hypomagnesemia: Causes of hypomagnesemia
- Hypomagnesemia: Clinical manifestations of magnesium depletion
- Hypomagnesemia: Evaluation and treatment
- Hypomagnesemia (FPNotebook)