Hypocalcemia: Low Blood Calcium Explained

Hypocalcemia means your blood calcium is lower than it should be. Calcium keeps nerves, muscles and the heart working. When it drops, you can feel anything from pins and needles to muscle cramps or strange heartbeats. Knowing the causes and what to do can prevent serious problems.

Causes and symptoms

Causes include low vitamin D, low parathyroid hormone after neck surgery, chronic kidney disease, severe magnesium deficiency, and some medicines like bisphosphonates or anticonvulsants. Symptoms often start vague: fatigue, muscle stiffness, or tingling around the mouth and fingers. If it gets worse you can get painful muscle spasms (tetany), tremors, seizures, or even changes on an ECG such as a prolonged QT interval. Kids and older adults may show different signs — babies can cry a lot and feed poorly.

Doctors check total serum calcium and correct it for low albumin, or measure ionized calcium directly. They also check magnesium, phosphate, vitamin D, and parathyroid hormone (PTH). An ECG is common if symptoms suggest the heart is affected. Labs tell whether the problem is due to low PTH, low vitamin D, kidney issues, or other causes.

Treatment and what you can do

Treatment depends on how low calcium is and how sick you are. Severe, sudden drops require emergency IV calcium (usually calcium gluconate) in hospital. Milder or chronic low calcium is treated with oral calcium supplements (calcium carbonate or citrate) and vitamin D (cholecalciferol or active forms when needed). If magnesium is low it must be fixed too, because low magnesium can stop calcium from going up.

Practical steps you can take: eat calcium-rich foods like milk, yogurt, cheese, fortified plant milks, canned fish with bones, and dark leafy greens. Get safe sun exposure and consider a vitamin D test if you have risk factors. Follow your doctor’s dosing for supplements — too much calcium raises the risk of kidney stones. Tell your provider about all medicines you take; some can lower calcium or interfere with vitamin D.

If you’ve had thyroid or parathyroid surgery, ask for calcium monitoring after the operation. For chronic conditions like kidney disease, work with your specialist on targets and medication adjustments. Recheck labs after starting treatment so levels and symptoms can be watched closely.

Go to the emergency room if you have severe muscle spasms, tingling that spreads quickly, trouble breathing, fainting, or seizures. These can signal dangerous low calcium. For milder symptoms, call your doctor and get a blood test.

Common medicines that affect calcium include loop diuretics (they can lower calcium), anticonvulsants like phenytoin (which lower vitamin D), and bisphosphonates after cancer treatment. Ask your doctor if any drug you take could be involved. When labs show low total calcium, doctors often correct the number for low albumin or measure ionized calcium directly to avoid confusion.

Typical follow-up checks happen within 1 to 4 weeks after starting treatment. With the right tests and a clear plan — diet, supplements, and fixing underlying issues — most people can get calcium back to normal and feel better.