Categories: Endocrinology

Why do you order Albumin with Calcium?

Total Calcium needs to be interpreted in the context of serum albumin levels 

WHY? Calcium is protein bound (primarily to Albumin). Hence in states of low or high albumin, the total Calcium level may not reflect the amount of ionized (free) Ca2+; which is the form that is physiologically active.

There are two formulas:

SI: Calcium (corrected) = Serum Calcium + 0.025 x (Normal albumin – Patient albumin) [sometimes the 0.025 will be approximated as 0.02]

*Normal albumin is typically 40g/L or 44g/L for most hospitals (US: 4g/dL or 4.4 g/dL)

US: Calcium (corrected) = Serum Calcium + 0.8 x (Normal albumin – Patient albumin)

Rule of Thumb: For every drop in 10g/L of Albumin, your total Calcium will increase by 0.2mmol/L (or 0.8 mg/dL)

NOTE: Evidence exists that the Payne correction formula does not correlate well with Ionized-Ca2+.

References

  1. Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973 Dec 15;4(5893):643-6.
Get Medical Pearls directly to your inbox every week!
Weekly posts with high yield medical knowledge, directly to your mailbox!
Dr. C Humphreys

Internal Medicine

Recent Posts

Why is Pro-BNP/ BNP lower in Obesity?

B-type natriuretic peptide (BNP) is a hormone created in response to cardiac wall stretch due…

4 months ago

What is Peribronchovascular Distribution on CT imaging?

A common finding described on computed tomography (CT) imaging. A disease with a peribronchovascular distribution…

11 months ago

Trapped Lung vs. Lung Entrapment

Though often used synonymously; Trapped Lung and Lung Entrapment technically describe separate entities along the…

1 year ago

Cause of Pericardial Effusion in Pulmonary Hypertension: Pathogenesis

It is not clearly understood why patients with pulmonary hypertension (PH) develop pericardial effusions. However,…

2 years ago

Difference between Mycophenolate Mofetil vs. Mycophenolate Sodium

The two drugs are not interchangeable nor dose equivalents. Mycophenolate mofetil (Cellcept) is a semi…

2 years ago

What is an “Anephric” Creatinine Rise?

Serum Creatinine can be a deceptive surrogate during an acute kidney injury. It may lag…

2 years ago

This website uses cookies.