Table of contentsWhat is calcium? – calcium symbolCalcium molar massNormal calcium levelsWhat is the corrected calcium?Corrected calcium equation – calculatorUnderstanding the calcium correctionCorrected calcium and pregnancyCalcium benefitsCalcium deficiencyLow calcium symptomsSources of calcium – foods high in calciumFAQs
This corrected calcium calculator is a simple tool that allows you to quickly assess calcium levels for patients with hypoalbuminemia (lowered levels of albumin). This article will help you answer the question, what is calcium, understand the difference between serum calcium and corrected calcium, and equip you with an easy-to-use corrected calcium equation.
We will also cover the topics of the calcium symbol and calcium molar mass, as well as what are normal calcium levels and when to suspect calcium deficiency based on the knowledge of low calcium symptoms.
Finally, we will show you foods high in calcium so that, by changing your diet, you can ensure calcium benefits for your body.
We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.
What is calcium? – calcium symbol
Calcium is an element with an atomic number of 20. In nature, it is present mainly in the form of calcium carbonate CaCO₃ in limestone and other rocks. We use calcium in the construction industry (calcium carbonate is an ingredient of cement, steelmaking, and in the production of automotive batteries and pipe cleaners.
Calcium is also essential for our bodies. It plays a massive role in maintaining proper bone growth as well as allowing blood, muscles, and nerves to function correctly. We have an entire hormone-producing gland (parathyroid gland) dedicated solely to maintaining adequate serum calcium levels! Keep reading to learn more about the optimal value of calcium for your body.
You will encounter the calcium symbol instead of the word calcium in many situations, like on the results of your laboratory tests, in formulas using a concentration of calcium, the notes of a fellow student (as a shortcut), or even on the periodic table of elements during chemistry classes. The calcium symbol is Ca – the first two letters of the word Calcium: CA-lcium. You may remember writing it while illustrating a chemical reaction between calcium and water, resulting in the creation of calcium hydroxide.
Ca + 2 H₂0 → Ca(OH)₂ + H₂
Calcium molar mass
Calcium molar mass is the weight of calcium (in grams) divided by its amount of individual atoms (in moles). A mole is a number of atoms or particles of a particular element or substance equal to 6.02214076 × 10²³ (you may recognize this as Avogadro's constant). Therefore, we can say that the calcium molar mass is the weight of 6.02214076 × 10²³ atoms of calcium. It is a fixed value – it measures precisely 40.078 g. Thus, the calcium molar mass is 40.078 g/mol.
We often use molar masses of different substances to determine how much of a product we will receive after performing a specific reaction. We use it on a daily basis in a branch of the chemical industry known as the theoretical yield. Laboratory technicians also need to know the calcium molar mass. They put it in an equation when they want to transform the level of serum calcium from mg/dl to mmol/l or from mmol/l to mg/dl.
Normal calcium levels
Normal calcium levels in a healthy adult should fall between 8.8-10.5 in mg/dL and 2.25-2.625 in mmol/L. A lower than normal calcium level is called hypocalcemia, while the state of higher than usual calcium levels is known as hypercalcemia.
Children can have lower and higher physiological calcium levels than adults (a broader range) because their bodies use calcium more intensively to grow bones. It is often assumed that the scope of normal calcium levels for children is between 7.6 mg/dl and 10.8 mg/dl (1.9 mmol/l and 2.7 mmol/l). For the normal calcium levels in pregnant women, see later on in this text.
What is the corrected calcium?
Most of the body's calcium is stored in the bones; the rest is contained in the blood. If the blood calcium level drops too low, the bones release calcium. On the other hand, if the calcium levels in the blood are too high, the extra calcium is either stored in bones or removed from your body in urine.
There is a problem with the regular serum test though: the calcium measured in your serum is not exclusively "pure" calcium. About 15% of it is bound to organic and inorganic anions, 45% is the biologically active ionized calcium. The rest – about 40% – is bound to albumin.
This relation means that we can underestimate the serum calcium levels for a patient with low albumin (hypoalbuminemia). For example, a patient with a very low albumin level and apparently "normal" calcium level can be suffering from hypercalcemia. To avoid such situations, you should estimate the corrected calcium level.
Corrected calcium equation – calculator
The method of calculating the corrected calcium levels is very simple. It was first described in the paper.
Corrected Calcium [mg/dL] = (0.8 × (Normal Albumin - Albumin)) + Calcium
Corrected Calcium [mmol/L] = (0.02 × (Normal Albumin - Albumin)) + Calcium
Normal albumin level is typically assumed to be equal to 4 g/dL.
The corrected calcium formula is not valid for patients with chronic kidney disease and end-stage renal disease (for more information on that subject, head to the GFR calculator).
There are many other tests on humans that we need to adjust for specific conditions. The results of a serum sodium level test may be incorrect due to hyperglycemia – too high blood glucose level. Visit our sodium correction calculator to learn more about it!
To perform a calcium-albumin correction using our calcium correction calculator, you have to follow these simple steps:
Measure your patient's serum calcium and albumin levels.
Serum calciumfield, type in the measured serum calcium level.
Analogically, in the field
Albumin, write your patient's serum albumin level.
You will get your result in the third field –
Corrected calcium. No need to perform calculations yourself and remember the complicated corrected calcium formula. Our corrected calcium calculator does it all for you!
Please remember that you can freely switch units of any typed in values (mg/dl or mmol/l – depending on the preferences of your laboratory).
Understanding the calcium correction
First, a quick recap. The levels of albumin and calcium in an adult patient should fall into the following ranges:
- Calcium: 8.8-10.5 mg/dL (2.25-2.625 mmol/L)
- Albumin: 3.5-5.5 g/dL (35-55 g/L)
Let's analyze the following example: you have a patient with low calcium levels (7.2 mg/dL) and exceptionally low albumin levels (1.1 g/dL). The calcium level suggests hypocalcemia. But should you, in fact, replace the calcium?
Start with using the corrected calcium calculator to obtain the corrected calcium levels. In this case, you are using mg/dl. Let's see how it looks when we put the data into the corrected calcium equation:
Corrected Calcium [mg/dL] = (0.8 × (4 - 1.1)) + 7.2 = 9.52
The corrected calcium level, in this case, is equal to 9.52 mg/dL. It means that the patient doesn't have to be treated for hypocalcemia. The low levels of calcium are, in this case, an indicator of hypoalbuminemia – this is the health issue that you have to address.
In a similar way, we perform a magnesium correction for albumin concentration. The results of a serum magnesium level test are also dependent on the patient's albumin level. See how you can do it with our corrected magnesium calculator!
Corrected calcium and pregnancy
You should also remember that the normal levels of calcium are different for pregnant women. You can use the following values as a rule of thumb:
- First trimester: 8.8-10.6 mg/dL (2.2-2.65 mmol/L)
- Second trimester: 8.2-9 mg/dL (2.05-2.25 mmol/L)
- Third trimester: 8.2-9.7 mg/dL (2.05-2.43 mmol/L)
Remember to adjust the results with the corrected calcium formula!
It is finally time to outline the value of calcium for our body and our health. Basically, we wouldn't be able to exist without it! Calcium benefits include:
Strengthening our bones – children with too low calcium levels (caused by a decreased vitamin D level) suffer from rickets, a disease in which there is reduced mineralization, causing the bones to be deformed.
Catalyzing (increasing the speed) of many biological processes in our bodies.
Regulating blood clotting – calcium is a part (number IV) of a so-called coagulation cascade – a process leading to fibrin formation. Fibrin, in turn, forms with blood platelets a hemostatic plug stopping bleeding.
Enabling contractions of muscles – a release of calcium ions (Ca²⁺) to the cytoplasm of muscle cells causes muscle contraction.
Facilitating correct conduction of neural impulses – calcium channels participate in creating the action potentials (depolarization) of neurons.
Calcium, in the form of calcium gluconate, may serve as a medication. And it is not solely used in the treatment of hypocalcemia! Healthcare workers can administer calcium gluconate when handling clinical situations like hyperkalemia (too high blood potassium level), hypermagnesemia (too high blood magnesium level), an overdose of calcium channel blockers and, because of its cardioprotective capabilities, to prevent cardiac arrest caused by electrolyte disturbances such as hypocalcemia, hyperkalemia, and hypermagnesemia. It requires, like every drug, careful dosing to avoid any side effects.
Calcium deficiency is defined as a lower than the normal physiological level of serum calcium. As you may remember from previous paragraphs, we call this state hypocalcemia. There are several reasons for calcium deficiency. We will mention a few of them:
An insufficient supply of calcium with our meals – we will talk about foods high in calcium in a later section.
A weak absorption of calcium inside our gastrointestinal system – this can be caused by intestinal diseases such as the malabsorption syndrome, too short intestines (e.g., after intestinal cancer surgery), or deficiency of vitamin D.
States in which calcium is binding and staying in soft tissues or bones. During acute pancreatitis – an inflammation of the pancreas, calcium binds by fatty acids creating their salts – soaps (the pancreas covered in a soap-like foam is a common sight for a surgeon operating on a patient with acute pancreatitis). Certain drugs (e.g., bisphosphonates used in the treatment of osteoporosis) also cause calcium to bind to bones.
Loss of calcium with urine – seen often in patients with kidney diseases or treated with diuretics – drugs causing increased urine production.
Too low vitamin D levels, caused by an insufficient supply of food, inadequate absorption, malfunctioning metabolism in the liver or kidneys, or an increased inactivation level.
Hypoparathyroidism – a disease of parathyroid glands in which they produce a decreased amount of parathyroid hormone. Parathyroid hormone (PTH) causes an increase in calcium in the blood. Thus, its deficiency results in lower calcium levels. Hypoparathyroidism often follows surgery on a thyroid gland as the parathyroid glands are very close to the tissue of the thyroid gland.
Tissues being resistant to the parathyroid hormone (PTH) – a genetic mutation of parathyroid hormone receptors in tissues. Although there is a high level of parathyroid hormone in the blood, it has little to no effect on the tissues and calcium release to the blood.
Errors of diagnostic tests measuring serum calcium. We have already covered one of them with our calcium correction calculator. In the state of low albumin level, one can have a misleadingly low serum calcium level. Another example of false hypocalcemia happens when we check calcium level not long after injecting a radiological contrast containing gadolin (used for MRI – magnetic resonance imagining).
You can perform some additional tests that can help you diagnose a patient with hypocalcemia: concentrations of creatinine, phosphates, magnesium, potassium, alkaline phosphatase, parathyroid hormone, and vitamin D. An abnormal result of any of these parameters may guide you to the pathology behind your patient's problem.
Low calcium symptoms
How does a person with hypocalcemia feel? We already know how calcium benefits us and its importance for our bones, blood, nerves, and muscles. Is the lack of calcium causing pathologies of these organs? Can one tell that a person is suffering from low serum calcium levels just from their symptoms or complaints? Well, an experienced clinician should be able to link the details from the patient's history and at least check their serum calcium level.
Here, we present low calcium symptoms:
Tetany – probably the most spectacular sign of low calcium levels. It consists of numbness and involuntary symmetric contraction of muscles. In the beginning, it affects the muscles of the hands, then forearms, arms, face (contraction of eyelids, lips in the shape of letter "o"), chest, and legs. It is important to note that the patient remains conscious all the time.
Chvostek sign – a clinical symptom checked by tapping at the emergence of the facial nerve on the patient's face (about 2 cm anterior to the ear). In the presence of a low calcium level, the muscles of the patient's face should contract to cause a grimace.
Trousseau sign – another clinical symptom. To perform this test, a clinician needs a sphygmomanometer (a device used to measure blood pressure). A doctor or a nurse puts it on a patient's arm and inflates it to reach a pressure 20 mmHg higher than the patient's systolic pressure. This causes an occlusion of the brachial artery and (in patients with hypocalcemia) cramps in the fingers of the tested arm.
Contraction of eyelids
Diplopia or a double vision – seeing two images of the same object simultaneously.
Photophobia – an intolerance of seeing the light, causing discomfort or pain in an eye when exposed to the light.
Contraction of bronchi – looking similar to an exacerbation of asthma. A person may have difficulty breathing and start to suffocate.
Contraction of the coronary, stomach, peripheral, and brain arteries. This may manifest in chest pain, like a heart attack, stomach pain, fingers turning white (the Raynaud symptom), or a migraine-like severe headache.
Prolongation of QT in an ECG test that may lead to severe arrhythmias. For more information on QT prolongations and their consequences, check our QTc calculator!
Sources of calcium – foods high in calcium
If you are suffering from a calcium deficiency, you need to get more calcium into your body! You can use some food supplements explicitly produced to treat calcium deficiency, but why don't you try modifying your diet first? If you look around, you will find many other rich sources of calcium, and you don't have to eat rocks and other minerals!
Here is our list of foods high in calcium that you can include in your dietary plan:
- Fruits and vegetables: collard greens, broccoli, kale, soybeans, figs, oranges, spinach, turnip greens, almonds;
- Dairy products: plain yogurt, milk, kefir, ice cream, and cheeses like ricotta, mozzarella, cheddar, feta, parmesan, or cottage cheese;
- Fish and seafood: sardines, salmon, mackerel, anchovies, shrimp; and
- Food enriched with calcium: fortified milk, orange juice, tofu, waffle, oatmeal, cereal, enriched cashew or rice beverages, and many others.
As you can see, there are many ways of modifying your diet with foods that are good sources of calcium, and it does not have to be boring at all! Let's see what a dietary plan (rich in foods high in calcium) of a person who wants to increase their calcium supply may look like.
- Breakfast: fortified cereals with milk, an orange to go.
- Second breakfast: plain yogurt or kefir (it can be served with cut figs for a better taste).
- Dinner: salmon prepared with almonds, rice, broccoli, and a bechamel sauce.
- Supper: a salad with spinach and some cheese, maybe feta?
What's the corrected calcium if albumin is 2 g/dL and serum calcium is 2 mg/dL?
The corrected calcium will be 3.6 mg/dL. You can calculate it using this formula:
corrected calcium = (0.8 × (4 − albumin)) + serum calcium
How do I calculate the corrected calcium?
You can calculate the corrected calcium in three steps:
- Determine the albumin level in g/dL.
- Calculate the calcium level in serum in mg/dL.
- Apply the corrected calcium formula:
corrected calcium = (0.8 × (4 − albumin)) + serum calcium
Why is corrected calcium important?
Corrected calcium gives a more accurate representation of the body's actual calcium levels, especially in situations where albumin levels may be abnormal, such as with malnutrition or liver disease.
What factors can affect corrected calcium levels?
Corrected calcium levels can be influenced by various factors including kidney function, vitamin D levels, medications like diuretics, and certain diseases like hyperparathyroidism.
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