- Normal Range
- 1.6 – 2.6 mg/dL
- Main Functions
- 60% STORED in bones & cartilage
- Skeletal muscle contraction
- Carbohydrate metabolism
- ATP formation
- Activation of vitamins
- Cellular growth
- DIRECT relationship with Ca++
- ETOH Abuse
- Renal Failure
- Excess intake of Mg-containing meds
- Overcorrection with Mg supplementation (IV or PO)
- Renal Failure
- *Fairly uncommon
- Neuromuscular → numbness/tingling, tetany, seizures, ↑ DTR’s
- CNS → psychosis, confusion
- GI → ↓ motility, constipation, anorexia
- EKG → prolonged QT
- CV → severe bradycardia → cardiac arrest, vasodilation, hypotension
- EKG → prolonged PR, Wide QRS
- CNS → drowsy, lethargic, coma
- Neuromuscular → slow/weak muscle contraction (watch Resp muscles!), ↓ DTR’s
- Replace Mg
- PO → Magnesium Hydroxide, NOT Magnesium Citrate (diarrhea)
- IV → 1g / hr (SLOW)
- Treat Cause
- d/c diuretics, aminoglycosides, phosphorus
- Monitor EKG & DTR’s
- Replace Mg
- Treat Cause
- d/c Mg-containing drugs or IV fluids
- Loop Diuretics
- Give Calcium Gluconate to protect heart
- Fluid & Electrolyte Balance
- Dietary restrictions or requirements
In this lesson we’re going to talk about Magnesium. We’ll look at what it does in the body and what happens when it’s too low or too high.
First, the normal range for Magnesium is 1.6 – 2.6 mg/dL. If you’re using the labs shorthand, you’ll see it here in this spot. The majority of magnesium in our body is stored in bones and cartilage. Magnesium has quite a few functions including skeletal muscle contraction of, carbohydrate metabolism, activation vitamins, ATP formation, and cellular growth. So, basically, without magnesium, you’re in big trouble. And, forgive the colloquialism, but you’re kind of up a creek without a paddle, if you know what I mean. One thing to know is that magnesium has a direct relationship with Calcium – so if one goes up, the other one usually does as well, and vice versa.
So, again, we’re going to look at what happens when it’s too low and too high. Let’s start with hypomagnesemia or low magnesium – less than 1.6 mg/dL. The most common cause of hypomagnesemia is alcohol abuse and renal failure. We could also see it in malnutrition or malabsorption issues, which is a big part of the problem with alcohol abuse as well. If our bodies can’t absorb the Magnesium we take in, then of course our levels will be decreased. We could also see low magnesium levels in hypoparathyroid because calcium. Remember that hypoparathyroidism causes hypocalcemia. Low calcium usually means low magnesium as well. The last common causes diarrhea, literally because magnesium is lost in the school.
Some of the symptoms of hypomagnesemia are very similar to symptoms of hypocalcemia, like numbness and tingling, tetany, and seizures, As well as increased deep tendon reflexes. We could also see significant confusion, decreased GI motility and constipation, and prolonged QT intervals on an EKG. Essentially, the nerve impulses are not able to move as quickly or as smoothly as they should.
Most of the time, we will treat hypomagnesemia by replacing magnesium slowly via IV. I mean super slow – we give no more than 1 gram of Mg per hour. You can replace it orally, but you have to make sure you’re using magnesium hydroxide, and not magnesium citrate, otherwise you are going to cause significant diarrhea, and further loss of magnesium. We will also want to treat the underlying cause and discontinue any medications that can decrease magnesium like diuretics or phosphorus. And, of course, we want to monitor our EKG rhythms and are deep tendon reflexes. One thing I want to note here in terms of clinical application is that low magnesium should always be treated before trying to replace potassium. In a state of hypomagnesemia, the body cannot absorb and process potassium that we administer. SO – we give Mag first or at LEAST at the same time as replacing K, otherwise the K we give does absolutely no good.
Now, let’s look at hypermagnesemia, which is when the level is greater than 2.6 mg/dL. This is actually fairly uncommon, the times we may see it usually involve excessive intake of drugs like magnesium-containing antacids, or overcorrection of low Mag levels. We could also see it in Acute Renal Failure. We know the kidneys are responsible for electrolyte regulation, so any time they aren’t working, we can see crazy alterations in basically all of our electrolytes, but again, high Mag levels are pretty rare.
Even though it’s fairly uncommon – high mag levels can actually be very dangerous and can lead to severe bradycardia and even cardiac arrest, plus vasodilation and hypotension. It can cause prolonged PR intervals and a wide QRS on the EKG as well as significant CND depression. It also causes muscle contraction to be very slow or weak – which can be dangerous when it comes to our respiratory muscles and trying to breathe efficiently. Even though it’s uncommon – It’s so important that you know this because the most common time we see these issues is when we OVERcorrect a low mag level or correct it too fast. So we need to make sure we’re replacing Mag SLOWLY or we can cause some really bad cardiac and CNS effects – you could really put your patient in danger. So remember, replace no more than 1 gram of Mag per hour.
Actually treating high mag levels usually involves treating or reversing the cause, discontinuing any drugs we’re giving that have magnesium in them, and possibly giving loop diuretics to try to excrete more Mag. In the meantime, we can also give Calcium Gluconate to protect the electrical systems of the heart.
Okay, so let’s recap. Normal value of magnesium is 1.6 – 2.6 mg/dL. Magnesium has MANY functions, including metabolism, muscle contraction, and nerve impulses, and it has a direct relationship with Calcium. Low Mag levels are usually caused by alcohol abuse, malnutrition and malabsorption, or acute renal failure – and could cause numbness and tingling, altered mental status and confusion, and slow GI motility and constipation. We want to replace Mag SLOWLY and to stop any losses the patient might be experiencing. High mag levels are rare, but most commonly caused by excessive intake or overcorrection of mag levels and could lead to cardiac or respiratory arrest and severe CNS depression. We want to stop any magnesium-containing medications, possibly give diuretics, and make sure we protect the heart. Other priorities are to treat the cause and to make sure we’re replacing Mag BEFORE we treat hypokalemia so that our bodies will actually retain the potassium we’re trying to give.
That’s it for magnesium, I hope this was helpful. Don’t miss all of our other electrolyte lessons and make sure you check out all the resources attached to this lesson. Now, go out and be your best selves today. And, as always, happy nursing!!