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Lab Values, part 3: Calcium (Ca)

Updated:
  • 00:00 Intro
  • 00:38 Function
  • 1:38 Expected Range
  • 3:14 Hypocalcemia
  • 5:45 Hypercalcemia
  • 7:51 Meris's Story
  • 11:47 Quiz
Cool Chicken Hint:

When you see this Cool Chicken, that indicates one of Cathy's silly mnemonics to help you remember. The Cool Chicken hints in these articles are just a taste of what's available across our Level Up RN Flashcards for nursing students!

This article is all about the lab value calcium: its expected range, causes and symptoms of higher and lower values, and a personal story from Meris about her experience with both hyper- and hypocalcemia at age 14.

This series follows along with our Lab Values Flashcards which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.

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What is calcium?

Calcium (Ca) is an important electrolyte for many physiological functions. Calcium is important for bone and teeth formation as well as nerve and muscle function. Calcium is also very important for clotting, because it is an integral part of the clotting cascade, including the intrinsic and the common pathways.

Calcium expected range

The normal range for serum calcium is 9 - 10.5 mg/dL.

Cool Chicken Hint:

California (CA) is due for a big earthquake, 9 - 10.5 on the Richter scale.

A note about exact lab values

Ranges will vary across sources. For example, you might be taught a normal range of 8.5 - 10.2 mg/dL for calcium. It's important not to get hung up on these small differences because if you're given a lab value that is out of range on your nursing exam, it's likely to be significantly out of range either on the high side (like 12 mg/dL) or the low side (like 7.0 mg/dL). It is unlikely they will give you a borderline lab value.

Check with your textbook, professor, or facility, to see what ranges you will be responsible for and what ranges you will be tested on.

Low calcium: hypocalcemia

Hypocalcemia means a low calcium level in the blood; below 9.0 mg/dL.

Hypocalcemia causes

Causes of low calcium can include hypoparathyroidism, acute pancreatitis, and vitamin D deficiency.

Hypoparathyroidism and hypocalcemia

The parathyroid glands' main purpose is to release parathyroid hormone (PTH). One of the main functions of the endocrine system and its hormones is to help the body achieve homeostasis in levels of hormones as well as electrolytes. PTH's main function is to increase calcium levels in the body (by contrast, calcitonin's main function is to reduce calcium levels in the body).

PTH increases calcium in three ways:

  1. PTH pulls calcium from the bones into the bloodstream.
  2. PTH causes increased reabsorption of calcium at the kidneys. Increasing reabsorption at the kidneys means you don’t lose as much calcium via urination.
  3. PTH causes increased absorption of calcium from food in the intestines.

Hypoparathyroidism is decreased/insufficient secretion of PTH. If the body is not producing enough PTH, the processes for increasing calcium are thereby hindered, resulting in hypocalcemia.

Vitamin D deficiency and hypocalcemia

Vitamin D is a fat-soluble vitamin required for calcium synthesis, so if vitamin D is too low, calcium levels can't be properly maintained by the body.

Hypocalcemia symptoms

Symptoms of hypocalcemia include a positive Chovstek's sign, a positive Trousseau's sign, muscle spasms, and paresthesia (a burning/prickling sensation).

Chvostek's sign and hypocalcemia

Chvostek's sign is an involuntary twitching of the facial muscles, typically around the nose/mouth, when the facial nerve is tapped or stimulated. The facial nerve is cranial nerve VII, which is both a sensory and a motor nerve. A positive Chvostek's sign can indicate hypocalcemia, but it is not foolproof, because it is sometimes absent in patients who have hypocalcemia, and sometimes present in patients who don't have hypocalcemia.

Trousseau's sign and hypocalcemia

Trousseau's sign is an abnormal reaction by the hand, to pressure on the arm. If you inflate a blood pressure cuff on a patient's upper arm and it causes spasms in their hands and fingers due to ischemia, that can indicate hypocalcemia. The spasm of the hand includes the wrist bending and the fingers coming together (similar to the closed version of the "blah blah blah" hand gesture).

Trousseau's sign is more reliable than Chvostek's sign as an indicator of potential hypocalcemia—it is more frequently present in patients with hypocalcemia, and less frequently present in patients without hypocalcemia, than Chvostek's sign is.

Muscle spasms and hypocalcemia

Because calcium is an electrolyte important for muscle function, including muscle contractions, low levels of calcium can lead to muscle spasms.

Paresthesia and hypocalcemia

Paresthesia means a burning or prickling sensation on the skin—like when your foot falls asleep. A burning/prickling sensation on the skin is usually related to nerves, and because calcium is important for nerve function, low levels of calcium (hypocalcemia) can lead to this sensation in some patients.

As Meris notes in the video, the sensation is often experienced in the fingers and toes but with hypocalcemia, a patient might also experience it around the mouth—this is known as circumoral paresthesia.

High calcium: hypercalcemia

Hypercalcemia means a high calcium level in the blood; above 10.5 mg/dL.

Hypercalcemia causes

Causes of high calcium can include hyperparathyroidism, cancer, prolonged immobility, and long-term corticosteroid use.

Hyperparathyroidism and hypercalcemia

Above, we discussed how hypoparathyroidism leads to underproduction of calcium. The inverse is also true. Hyperparathyroidism can lead to overproduction of calcium, resulting in hypercalcemia. The parathyroid glands produce parathyroid hormone (PTH), which stimulates calcium production. If the body's level of PTH is too high as a result of hyperparathyroidism, calcium production will be in overdrive, which can result in hypercalcemia.

Cancer and hypercalcemia

Malignant is a term used to describe cancer. Mal- is a prefix that means bad (e.g., malfunction, maladjusted, malodorous, Maleficent the villainous witch from Sleeping Beauty). We created our Medical Terminology flashcards to make breaking down words into their parts easy, so you never have to be confused by an unfamiliar word on an exam!

When applied to cancer or a tumor, malignant means it is growing in an uncontrolled way, invading nearby tissues, and causing destruction.

A malignant tumor or cells can break down bone (bone metastasis), which leaches calcium into the blood.

Prolonged immobility and hypercalcemia

Prolonged immobility can cause hypercalcemia. As Meris notes in the video, this is very important for the NCLEX test and for general clinical practice. Prolonged immobility means little stress or weight is put on the bones, which can lead to bone demineralization ("use it or lose it"), which liberates calcium from the bones into the blood, thereby raising blood calcium.

Immobility also affects the respiratory, cardiovascular, gastrointestinal, renal, integumentary and psychosocial systems—for more on immobility, check out Fundamentals - Practice & Skills Immobility and Deep Vein Thrombosis.

Long-term corticosteroid use and hypercalcemia

Another cause of hypercalcemia can be long-term corticosteroid use. Over time, corticosteroids can reduce osteoblast (bone-building) activity and increase osteoclast (bone demolition) activity. Anything that causes bone resorption is usually linked to hypercalcemia, as the calcium from the bones is then liberated into the bloodstream.

Long-term corticosteroid use (and/or the abrupt discontinuation of corticosteroid therapy in a patient with Addison's disease) can also result in adrenal insufficiency, which means the adrenal cortex isn't producing enough aldosterone, and when aldosterone is low, this can lead to dehydration, including high BUN and high calcium.

Hypercalcemia symptoms

Symptoms of hypercalcemia include kidney stones, GI upset, constipation, bone pain, muscle weakness, and confusion.

Kidney stones and hypercalcemia

One important symptom of hypercalcemia is the presence of kidney stones.

First of all, let's give a major shoutout to the humble kidney. The kidneys do multiple important jobs, not the least of which is filtering our blood from waste products. In general, the kidneys take in blood containing waste, filter that blood, turn the waste into urine and return the filtered blood and its electrolytes to the rest of our body.

With hypercalcemia, the kidneys attempt to filter and excrete the excess calcium, but it's hard work, and the extra calcium can build up in the kidneys and cause renal calculi AKA kidney stones.

GI upset/constipation and hypercalcemia

In the section on hypocalcemia, we discussed involuntary muscle spasms, like Trousseau's sign. Low calcium can lead to muscle excitability.

The opposite is also true: too much calcium can lead to muscle inexcitability. When muscles are inexcitable, involuntary muscle contractions are slowed. Gastric motility (digestion; food moving through the GI tract) is powered by coordinated, involuntary muscle contractions. When too much calcium is present (hypercalcemia), gastric motility is hindered, which can result in GI upset and constipation.

Bone pain and hypercalcemia

Most of the body's calcium is stored in the bones, as opposed to the blood. In the case of immobility described above, bones leaching calcium into the bloodstream can be the cause of hypercalcemia. If the bones are dumping their calcium into the blood, the bones themselves aren't left with enough calcium to maintain their ideal structure or strength, which can lead to bone pain.

Muscle weakness and hypercalcemia

What's the connection between muscle weakness and hypercalcemia? As we discussed above, hypercalcemia can lead to muscle inexcitability; when a patient attempts to work muscles that are inexcitable, it will be a slog!

Confusion and hypercalcemia

Remember that an appropriate level of calcium is required for both muscle and nervous system function. Neurons and their neurotransmitters, which are required for thinking, are part of the nervous system. Just like hypercalcemia can cause muscle inexcitability, it can also cause neuron inexcitability. When your neurons can't fire properly, you can't think. That's how hypercalcemia can lead to confusion.

Meris's experience with hypercalcemia

When Meris was 14, she was having symptoms of hypercalcemia — "stones, bones, psychic moans, GI overtones." This meant bone pain (severe, deep pain in the bones); severe GI issues (near-constant stomach pain and constipation); weakness, including exhaustion and sleeping all the time; and psychiatric disturbances including strange personality changes (beyond the expected for a 14-year-old).

Meris went to the doctor and they discovered she had 21 stones in both of her kidneys. They were able to diagnose her with hyperparathyroidism, with a benign tumor on one of her parathyroid glands. This was unusual for a 14-year-old; usually those affected are postmenopausal.

Meris underwent a parathyroidectomy, a removal of one of her parathyroid glands. Most people have 4 parathyroid glands, and when one of them has a tumor, it's working in overdrive, so the other glands are basically asleep. So after her parathyroidectomy, it took some time for Meris's other three parathyroid glands to wake up and realize they were supposed to be doing something.

During that time, Meris's calcium level plummeted. So, she went from having hypercalcemia to hypocalcemia. She experienced the circumoral paresthesia described above. She visited the emergency room and they treated her, and then she was feeling better.

Today, Meris has two reminders of this experience—a scar across her neck from her parathyroidectomy surgery, and a tattoo of a kidney with stones.

Full Transcript: Lab Values, part 3: Calcium (Ca)

Hi, I'm Meris, and in this video, I'm going to be talking to you about the lab value calcium. I'll be talking to you about the expected range and the causes and symptoms of higher or lower values of calcium. I'm going to be following along using our lab values flashcards. These are available on our website, leveluprn.com, if you want to grab a set for yourself. Or if you are more of a fan of digital products, I would invite you to check out Flashables, which is the digital version of all of our flashcards available right now on demand in your pocket wherever you go. All right. Let's go ahead and get started.

So first up, let's just talk about what calcium is and why it matters to the body. So calcium is going to be a very, very important electrolyte for our body when it comes to many physiological functions. Big one here being bone and teeth formation along with nerve and muscle function. But it does have an important role in many different functions in the body. Now, one of the things that it also has a role to do with that I think gets left out of the conversation a lot is clotting. And as a trauma nurse, this is why calcium matters a lot to me, is that it is also an integral part of the clotting cascade in two separate locations. So just remember that calcium, we think about bones and teeth, and it's super important for that. But there are other functions that calcium has as well. And for me, for my purposes, blood clotting is one of them.

Now, let's talk about the expected range for calcium. We have to know what we expect an average human being to fall in when we're talking about these ranges. So for calcium, in particular, we are talking about 9 to 10.5 milligrams per deciliter. 9 to 10.5. And we do have a cool chicken hint here on the card for you to help remind yourself of this value because it can be tricky to remember all of these little values and what their normal ranges are. So we came up with some ways to remember. And our cool chicken hint here is California, CA, is due for a big earthquake, 9 to 10 and a half on the Richter scale. So that's one way that you can remember it. But we actually have two ways. We have two cool chickens here. The other one is to call, CA, call 911. So call 911. It's going to tell you 9 to 11. It's just helping you to remember the general range, but you're going to have to remember that that maximum top number is 10. 5. Again, with any lab value that we are talking about, though, all of these are subject to your textbook, your lab, your facility. Just know that this is what we found as the best general consensus on what these lab values should be.

Now, what happens if I have hypocalcemia? And I'm going to tell you a personal story about myself as we progress through this video because I hope that it will help you to remember. Hypocalcemia, we have low calcium in our blood, meaning we are below 9 milligrams per deciliter. If I have hypocalcemia, some of the causes here could be hypoparathyroidism, acute pancreatitis, and then vitamin D deficiency. If I don't have enough vitamin D, I cannot synthesize whatever calcium I have. I cannot get it where it needs to go. So vitamin D insufficiency can lead to hypocalcemia as well. What are some symptoms, though, of hypocalcemia? Well, the big ones here are going to be a positive Chvostek's and Trousseau's sign, and I'm going to talk to you briefly about these.

Chvostek's sign is where I tap on the facial nerve of my patient on one side or the other. I tap on the facial nerve, and I look to see, is there any twitching on that side? If I tap here and see twitching, that is a positive Chvostek's sign. This is not our official cool chicken hint, but the way I remember the difference between the two is C for Chvostek's. I think C for cheek. Now, Trousseau's sign. Trousseau's sign is very interesting. I've only ever seen it once, but the way that you will observe it is we will put a blood pressure cuff on and inflate that blood pressure cuff. And while it is inflated, you will watch their hand. I'm going to bring it up so you can see. You will watch their hand begin to do this. They will have a carpal spasm, and it gives them kind of this appearance of their limb while the blood pressure cuff is inflated. That is called Trousseau's sign, and that would be a positive finding. That would be an abnormal finding. So both of these are present in hypocalcemia. Super, duper important things to know in relation to one another and in relation to that electrolyte imbalance. So aside from Chvostek's and Trousseau's sign, what else might we be seeing in somebody who has hypocalcemia? Muscle weakness? Absolutely possible. And then paresthesias. Paresthesias are those pins and needles or that burning, prickling sensation. Very common to have it in the fingers and toes, but with hypocalcemia, they can also experience it around the mouth. We call that circumoral paresthesia.

Now, on the flip side, what if I have too much calcium? Well, what are some possible causes of hypercalcemia? Some causes would be the opposite of what causes hypocalcemia. So hypocalcemia goes with hypoparathyroidism. Hypercalcemia goes with hyperparathyroidism. If I have an overactive parathyroid gland, it is going to take all of the calcium out of my bones and dump it into my blood, thereby raising my serum calcium. Okay? Some other possible causes of hypercalcemia, cancer. This is a very big one. Malignancy can lead to elevated calcium. Prolonged immobility. This is hugely important for the NCLEX test-taking world and for your general clinical practice. If I have somebody who is in a state of prolonged immobility, they're not stressing their bones, they're not putting any weight on their bones, their body will say, "I guess they don't need to be so dense," and they'll start to chew up their bones, liberating calcium into the blood, thereby raising your patient's blood calcium. Some other considerations too would be long-term corticosteroid use. This is an important one to know for some other NCLEX things as well.

Now, what are some symptoms that I might see in somebody who has - I'm sorry - hypercalcemia? Here's some symptoms from our list. Kidney stones. Kidney stones is a huge thing for you to consider because if I have too much calcium in my blood, it's going to go to my kidneys. My kidneys are going to filter it out. That calcium is going to start to collect in my kidneys. And then before you know it, you're going to have a kidney full of stones, just like this one that I have back here on my arm. Kidney stones are absolutely a possible outcome of hypercalcemia. GI upset, including constipation, bone pain, muscle weakness, and confusion. Now, I told you I was going to tell you a personal story about me, and this is the story that I always tell to students. This is the story that I tell about the time I almost died from hypercalcemia. So when I was 14, I suffered from hyperparathyroidism. We did not know it at the time. The way that it was diagnosed was due to the findings associated with hypercalcemia. Okay? I was 14 years old. I was way too young to have hyperparathyroidism. This is normally a condition that affects people who are postmenopausal. So this was very unusual for me to have this benign tumor on my parathyroid.

What happened was all of the calcium got leached out of my bones and dumped into my blood, and I had a calcium level that was so high that it could not be read by the laboratory. It only resulted as high. Let me tell you what my symptoms were. My symptoms were very classic stones, bones, psychic moans, GI overtones. So I had bone pain, severe deep pain in my bones, which came from the liberating of the calcium. It is painful to have your bones chewed up by those osteoclasts. I also had severe GI problems, belly pain all the time, constipation. I was incredibly weak. I was exhausted. I slept all of the time. And I had some psychiatric disturbances as well, some things that just caused me to have strange behaviors, strange personality changes. Finally, I was diagnosed because I had a kidney full of stones. And that's why I have this tattoo back here of this kidney full of stones. It's because when I was 14, they found I had something insane in my kidneys, like 21 stones in both of my kidneys. Again, because I had been hypercalcemic for so long. It was identified that I had hyperparathyroidism, which is why I have this scar across my neck here is because I had a parathyroidectomy. I had a removal of my one affected parathyroid gland.

When you take out a parathyroid gland, it takes some time for the others to wake up. So they took it out, and it took time for my other three parathyroid glands to perk up and say, "Oh, we're supposed to be doing something." During that time, my calcium level plummeted because we got rid of the bad parathyroid, and now nothing was happening. So I went from being hypercalcemic to profoundly hypocalcemic. And I knew I needed to go to the hospital when I couldn't control my legs, by which I mean I wanted them to move. I was trying to move them. They were not moving. Muscle weakness, remember? And I had paresthesias around the mouth in particular. I had circumoral paresthesia. I went to the ER. They drew my blood and said, "Yes, absolutely. She's very low on calcium." They remedied the situation, and I felt much better. So when you think of hypercalcemia, I want you to think of me before diagnosis, GI problems, sleep disturbances, bone pain, weakness, just psychiatric disturbances, and kidney stones. And then when you think of hypocalcemia, I want you to think about little 14-year-old me on the couch saying, "Mom, I'm trying to move my feet, but they won't move." I was so profoundly weak and had such significant nerve and muscle dysfunction that I was unable to move my little feet, and I had paresthesias around the mouth.

All right. I'm so glad you stayed until the end, not just so you could hear my story about hyper and hypocalcemia, but because I'm going to test your knowledge of some key facts I provided in this video with my quiz questions.

The nurse is caring for a patient experiencing hyperparathyroidism. Which electrolyte imbalance should the nurse anticipate?

Hypercalcemia.

While caring for a patient, the nurse suspects they may be experiencing hypocalcemia. The nurse taps on the patient's facial nerve, which causes their face to twitch. What has the nurse just observed?

A positive Chvostek's sign.

All right. That is it for this video. I hope you learned something and found it useful. Thanks so much, and I'll see you next time.

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