There are different units of measure for blood calcium, parathyroid hormone, and vitamin D. Different countries use different measures, sometimes different laboratories in the same country use different measures. One is not better than the other. Just as we can report our weight in pounds or kilograms, we can report blood calcium levels in mg/dl, or mmol/L. Similarly, just as we can measure distance in miles or kilometers, we can measure PTH levels in pg/ml or pmol/L. This app was designed to allow all users to enter their data in whichever way it came; the app will automatically convert between the different units.
The normal range for blood calcium is different for children than it is for adults. Children and teens have higher amounts of calcium in their blood than adults because they have the highest level of bone metabolism and are actively forming new bone all the time. Adults over 25 years of age stop forming bone and therefore the upper limit of calcium begins to come down. Adults over 35 years of age have the lowest levels of blood calcium; this is normal because they are no longer forming new bone. Most reports of blood calcium do not account for your age and therefore reports the upper limit for all people, including children. This is unfortunate because many older adults with hyperparathyroidism are not recognized early when their calcium begins to rise because the lab values are treating the adult like he/she is a teenager—the results will say that a calcium up to 10.7 mg/dl (2.67 mmol/L) is normal, but this is normal for children and teenagers, not for adults. This app requires your age because there is no way to interpret a person’s calcium levels without knowing their age. The normal values and many of the graphs in this app will change according to your age. In fact, if you change the year of your birth so you are 18 years old, the graphs will change quite a bit! Teach this to your doctors!