The card shows an example result of 2.9, which is 2.50 SD above the mean.

What it measures

Serum calcium divided by serum phosphorus, both in mg·dL⁻¹. Bone needs both minerals in balance, and hormones such as PTH and vitamin D keep them there.

Reference range

The mean is (low + high) / 2 and the SD is (high − low) / 4, so the healthy range covers Z from −2 to +2.

Reading the result

• High — Can point to high calcium or low phosphorus, as with an overactive parathyroid gland.
• Low — Can point to low calcium or high phosphorus, as with kidney disease or low vitamin D.

Notes

• The middle of the range is best, so both sides are flagged.
• As a ratio, it has no unit. Look at calcium and phosphorus separately too.
• This page is general information, not medical advice. Discuss results with a clinician.