Multiple myeloma and hypercalcemia: Link, causes, and more

Multiple myeloma is a blood cancer that loves bones a little too much. Instead of simply hanging out in the bone marrow like a polite guest, myeloma cells
disrupt normal bone remodeling, drill tiny “holes” in bones, and spill calcium into the bloodstream. That calcium overload is called
hypercalcemia, and it can turn into a medical emergency if it’s not caught and treated quickly.

Hypercalcemia isn’t rare in myeloma. Studies suggest that around 10–20% of people with multiple myeloma have high calcium levels at diagnosis, and more than a
quarter will experience it at some point during their disease course. In fact, elevated calcium is one of the classic “CRAB” features doctors look for when
confirming active, symptomatic myeloma: Calcium elevation, Renal (kidney) problems, Anemia, and
Bone damage.

What are multiple myeloma and hypercalcemia?

Multiple myeloma in a nutshell

Multiple myeloma is a cancer of plasma cellsimmune cells that normally make antibodies to fight infections. In myeloma, these cells become abnormal,
multiply uncontrollably, and crowd the bone marrow. They interfere with normal blood cell production and release proteins and signals that affect bones,
kidneys, and the immune system.

The most common problems linked to myeloma include:

• Bone pain and fractures
• Anemia (low red blood cells) and fatigue
• Frequent infections due to immune suppression
• Kidney damage from myeloma proteins and high calcium
• Hypercalcemia (high blood calcium levels)

What is hypercalcemia?

Calcium is crucial for strong bones, muscle contraction, heart rhythm, and nerve function. In hypercalcemia, the level of calcium in the
blood is higher than normal. Mild elevations may cause few or no symptoms, but moderate to severe hypercalcemia can lead to constipation, nausea, confusion,
kidney issues, and even life-threatening heart rhythm disturbances or coma if not treated promptly.

In people with cancer, especially multiple myeloma, this is often called hypercalcemia of malignancy, one of the most serious oncologic
emergencies adults can face.

How are multiple myeloma and hypercalcemia linked?

Bone destruction: when myeloma turns bones into “calcium donors”

In healthy bone, there’s a constant balance between cells that build bone (osteoblasts) and cells that break it down (osteoclasts). Multiple myeloma throws
this balance off. Myeloma cells and surrounding bone marrow cells release signaling moleculessuch as those that activate the RANK/RANKL pathwaythat
stimulate osteoclasts and suppress osteoblasts. As a result, bone is broken down faster than it’s rebuilt, creating lytic (hole-like) lesions and releasing
calcium into the bloodstream.

The more extensive the bone involvement, the greater the risk that enough calcium will spill into the blood to cause hypercalcemia. Kidney problems, which
are also common in myeloma, can make it harder for the body to get rid of the extra calcium, compounding the issue.

The “C” in CRAB: why high calcium is such a big deal

Elevated calcium is built into the diagnostic criteria for active multiple myeloma. The International Myeloma Working Group includes high blood calcium
(usually defined as a serum calcium level more than 1 mg/dL above the upper limit of normal, or >11 mg/dL) as one of the key signs of organ damage that
signals the need for treatment.

Clinically, hypercalcemia is also a red flag. It’s associated with:

• More advanced disease and heavier tumor burden
• Worse kidney function and dehydration
• Shorter overall survival in some studies

In other words, when calcium goes up in myeloma, doctors pay very close attention.

How common is hypercalcemia in multiple myeloma?

Hypercalcemia is one of the more frequent complications of myeloma compared with many other cancers. Large studies suggest:

• Roughly 10–15% of people have high calcium at the time myeloma is diagnosed.
• More than 25% will experience hypercalcemia at some point in their disease course.
• In some myeloma cohorts, around 17–21% have hypercalcemia as a presenting feature of symptomatic disease.

Among all cancers, hypercalcemia of malignancy tends to be most common in multiple myeloma and certain solid tumors like lung or breast cancer.

Signs and symptoms: what hypercalcemia feels like

Hypercalcemia symptoms often follow the classic “stones, bones, groans, and psychiatric overtones” pattern, but that doesn’t always appear neatly in
real life. Some people have very high calcium and barely feel it; others feel terrible with only a mild rise.

Common early symptoms

• Fatigue, feeling unusually tired
• Weakness or heavy-feeling muscles
• Constipation or fewer bowel movements than usual
• Loss of appetite, nausea, or mild abdominal discomfort
• Increased thirst and peeing more often (especially at night)
• Difficulty concentrating, “brain fog,” or mild confusion
• Irritability, low mood, or personality changes

More severe or urgent symptoms

• Vomiting or severe abdominal pain
• Severe confusion, agitation, or drowsiness
• Dehydration and dizziness, especially when standing
• Irregular heartbeat or palpitations
• Worsening kidney function, sometimes with swelling in the legs or decreased urine output
• In extreme cases, stupor, coma, or life-threatening arrhythmias

Because some of these symptoms can also come from chemotherapy side effects, infections, or the myeloma itself, it’s easy for hypercalcemia to be missed
without blood tests. That’s why regular monitoring is so important in people with myeloma.

How doctors diagnose hypercalcemia in myeloma

The diagnosis starts with a simple blood test measuring total serum calcium, often corrected for albumin levels or replaced/confirmed by measuring
ionized calcium (the active form). Other labs can include kidney function tests, electrolytes, parathyroid hormone (PTH), vitamin D, and, of course,
myeloma-specific tests such as monoclonal protein levels and bone marrow evaluation.

Imagingsuch as whole-body low-dose CT, PET-CT, or MRImay be used to look for bone lesions that indicate active myeloma and help explain why calcium is
elevated. Together with CRAB features and myeloma markers, these tests help confirm that the high calcium is due to myeloma rather than another cause like
overactive parathyroid glands or certain medications.

Treatment: how hypercalcemia is managed in multiple myeloma

Treating hypercalcemia in multiple myeloma has two main goals:

1. Bring calcium back into the normal range quickly and safely.
2. Control the underlying myeloma so the calcium doesn’t keep spiking.

Emergency and short-term treatments

For moderate to severe hypercalcemia, treatment is usually done in the hospital. While the exact approach varies by patient, common strategies include:

• Intravenous (IV) fluids: Often normal saline to correct dehydration and help the kidneys flush out extra calcium.
• IV bisphosphonates: Medications like zoledronic acid or pamidronate slow bone breakdown and reduce calcium release from bone; they work
  over several days.
• Calcitonin: A hormone that lowers calcium more quickly, used as a short-term “bridge” while other drugs take effect.
• Glucocorticoids (steroids): Especially helpful when hypercalcemia is related to certain mechanisms; they can reduce bone resorption and
  lower calcium in some myeloma patients.
• Denosumab: A targeted therapy that blocks RANKL, an important driver of osteoclast activity. It’s especially useful when kidney function
  is poor or when bisphosphonates are not enough.
• Dialysis: In very severe cases, or when kidney failure is present, dialysis may be needed to clear excess calcium.

Long-term control: treating the myeloma itself

Hypercalcemia usually improves and stays under better control when the underlying myeloma is treated effectively. Modern myeloma regimens may include:

• Proteasome inhibitors
• Immunomodulatory drugs
• Monoclonal antibodies
• Steroids
• Chemotherapy and, for some, stem cell transplant

When myeloma shrinks, bone destruction slows down, and calcium levels typically stabilize. Anti-resorptive drugs (like bisphosphonates or denosumab) are
often continued on a scheduled basis to protect bone and reduce the risk of fractures and future calcium spikes.

Living with multiple myeloma and hypercalcemia

Monitoring and everyday strategies

For people living with myeloma, routine blood tests are your early-warning system. Regular monitoring helps catch rising calcium levels before symptoms
become severe. Depending on your situation, your care team may also:

• Adjust medications that can raise calcium levels or stress the kidneys.
• Encourage adequate (but not excessive) fluid intake, if your heart and kidneys allow.
• Recommend physical activity, as tolerated, to support bone health and overall function.

Diet alone rarely causes hypercalcemia in myeloma, but your team may talk with you about supplements and vitamin D use. It’s important not to start or
stop supplements without checking with your oncologist or hematologist, especially if your calcium has been high in the past.

When to call your care team right away

Get urgent medical advice or emergency care if you have multiple myeloma and you notice:

• Sudden or severe confusion, extreme sleepiness, or unusual behavior
• New or rapidly worsening nausea, vomiting, or abdominal pain
• Very little urine output, or swelling in your legs and feet
• New or worsening chest pain, shortness of breath, or palpitations
• Severe dehydration symptoms: dry mouth, dizziness, inability to keep fluids down

These symptoms don’t always mean hypercalcemia, but they are serious and need prompt evaluation.

Experiences and practical insights: living with the link between myeloma and high calcium

Statistics and lab values are important, but they don’t tell the whole story of what it’s like to live with multiple myeloma and hypercalcemia. In the real
world, people often describe the experience less in medical terms and more in everyday language: “I felt like my brain was wrapped in cotton,” or “I just
couldn’t shake the exhaustion, no matter how much I slept.” Fatigue, fogginess, and subtle mood changes are some of the earliest clues that something is off
with calcium levelslong before a person learns the term “hypercalcemia.”

One common theme patients report is how easily hypercalcemia symptoms can be mistaken for other parts of the cancer journey. Constipation? That could be
pain medicines. Nausea? Maybe chemotherapy. Confusion or trouble concentrating? It might be stress, insomnia, or “chemo brain.” Because the symptoms overlap
with so many other issues, many people only find out their calcium is high when routine labs or an emergency room visit reveals it. That’s one reason
providers place so much emphasis on scheduled blood work and prompt reporting of new or changing symptoms.

On the flip side, many patients describe an almost startling improvement once hypercalcemia is treated. After a few days of IV fluids, medication, and rest,
that heavy, sluggish feeling begins to lift. People sometimes say they feel “clearer” or “more like themselves” againproof that high calcium doesn’t just
affect bones and kidneys; it affects how you think, move, and connect with others. Even small improvements in concentration or energy can make daily tasks,
conversations, and self-care much easier.

Caregivers also play a crucial role here. They are often the first ones to notice when something is “off”perhaps a loved one is more forgetful, irritable,
or unsteady on their feet. Caregivers may be the ones who call the clinic and say, “This isn’t normal for them.” Keeping a short symptom journal, even just a
few bullet points each day, can help track subtle changes over time and give the care team concrete examples to respond to.

Another practical insight from many patient and caregiver stories is the importance of hydration. While fluid recommendations must always be tailored to
heart and kidney status, people who are able to drink regularly often feel better overall and may reduce the severity of dehydration when hypercalcemia
occurs. Setting reminders to sip water throughout the day, keeping a favorite bottle nearby, or linking drinking habits to daily routines (like taking
medications or mealtimes) can help. Some people also find that limiting sugary beverages or heavy caffeine makes it easier to notice when they’re genuinely
thirsty and to avoid additional kidney stress.

Emotionally, coping with both myeloma and hypercalcemia can feel like juggling two crises at once. There’s the long-term reality of living with an
incurable (but increasingly treatable) cancer, and then there are sudden episodes like a calcium spike that may require urgent hospitalization. Many people
say it helps to think of hypercalcemia management as part of the larger treatment plan, not as a separate “failure” or setback. When framed this way,
treating high calcium becomes another tool in the fight: bring the numbers back into range, protect the kidneys and heart, and keep the body strong enough
to tolerate the myeloma therapies that are working behind the scenes.

Finally, connection matters. Whether it’s a local support group, an online community focused on multiple myeloma, or conversations with other patients met
during infusion visits, learning how others have navigated episodes of hypercalcemia can be both reassuring and practical. People share tips about what to
pack for a hospital stay, how to talk with employers or family members about sudden health changes, and how to advocate for timely lab checks when symptoms
flare. While every journey is different, those shared experiences can turn confusing terms like “CRAB criteria” and “hypercalcemia of malignancy” into
something more understandableand more manageablein daily life.

If you or a loved one are living with multiple myeloma, it’s worth asking your care team how often your calcium is checked, what symptoms they want you to
report right away, and what the plan would be if your levels suddenly rose. Having that plan in place doesn’t eliminate the risk of hypercalcemia, but it
can transform a frightening unknown into a challenge you’re ready to face with information, support, and a clear path forward.