Corrected Serum Calcium

  1. hello, I am trying to understand corrected calcium, and I am really confused. I understand that Ionized Ca is the only physiologically important form of Calcium, and I understand that Calcium and Albumin have an important relationship. I was taught that Ionized Ca samples aren't often not handled correctly, because they are pH dependent, therefore, it is wise to calculate a corrected Ca.To measure the corrected Ca,

    (0.8*(Narmal Albumin - Pt's Albumin)) + Serum Ca

    What I am not finding, is how to interpret these results. I think I understand everything else, but what do I do with the result? When do you replace Ca? I've looked in my books, online etc...If anyone can help, I'd greatly appreciate it. My Patho instructor has not been available to clarify this.

  2. Visit cruisin_woodward profile page

    About cruisin_woodward

    Joined: Feb '09; Posts: 333; Likes: 222
    Orthopedic Nurse Practitioner; from US
    Specialty: CT ICU, OR, Orthopedic


  3. by   BCgradnurse

    In my previous life (before becoming a FNP) I was a medical technologist, so hopefully I can help. You are correct in that ionized calcium specimens have to be drawn in the correct tube as specified by your lab, and must be tested promptly to insure an accurate result. A corrected calcium has the same normal values as regular calcium, usually around 8.7-10 (lab specific). You're just adjusting for the patient's albumin levels. Hope this helps.
  4. by   TX RN
    I can probably best explain it by presenting an example.

    Patient W has the following lab values
    Na 140
    K 4.0
    Ca 7.4 mg/dL
    Albumin 1.2 g/dL

    Now, the question is should you replace the calcium?

    The corrected calcium in this scenario = 9.64 mg/dL
    Here's the formula:
    Corrected calcium = (0.8 x (Normal Albumin (4.0 g/dL; 40 g/L) - Serum Albumin)) + Plasma Ca

    My understanding is that you use the corrected calcium to determine if a calcium disorder needs to be treated. Essentially, you use the corrected calcium level instead of the serum calcium in your evaluation of the patient.

    If the level is normal then you don't treat the hypocalcemia, such as in this case above, corrected calcium falls in the normal range.

    The low measured level of serum calcium is a manifestation of low albumin levels. Your course of action should be to address the low albumin levels, nutritional status of your patient. Replacing the calcium will be of no benefit to your patient.

    If the corrected calcium level is in fact low and reveals that your patient truly is hypocalcemic then your course of action would be to treat. Usually a vit D defficiency and or maybe a hypoparathyroid disorder.
    Last edit by TX RN on Dec 20, '09
  5. by   cruisin_woodward
    Thank you both so much! That is exactly what I needed. My exam is tomorrow, and I was really stuck on this! I understand FINALLY!!
  6. by   traumaRUs
    Corrected calcium is very important too when a pt has renal failure because nephrology pts run much lower Ca - in the 7.4-8.3 range.

    I rarely replace calcium unless my pt is I have dialysis pts that run in the 5.5 to 7 range all the time.
  7. by   cruisin_woodward
    Thanks everyone! It wasn't on my exam, but I needed to know it for clinical practice too, so I appreciate all of the input!
  8. by   BmoreCRNP
    This was very helpful to me as well. I work in LTC, and some of my patients have low Calcium. Usually it's in the high 7's to low 8's. In addition to that, a lot of LTC patients have low albumin levels. The dietician is usually the one who deals with that and often places the patient on a protein replacement shake or something of that nature. I don't usually correct hypocalcemia either, as it has usually self corrected OR it's been that way for a long time and the patient was never symptomatic.
  9. by   globalRN
    for those who use SI units...the rest of the world other than the usa

    (40- serum albumin)x0.025

    add this result to the serum calcium