Phosphate
What it measures, and what changes the number.
Phosphate is a mineral found mostly in bone, with the rest involved in energy handling inside cells and in acid balance. This test measures the inorganic phosphate in serum or plasma; some labs call it phosphorus, though the measurement is the same.
It is typically read with calcium, parathyroid hormone and vitamin D (25-OH), since these work together to regulate bone minerals, and with creatinine because the kidneys control how much phosphate is kept or excreted. Magnesium is often included in the same panel.
The level shifts through the day and tends to drop after meals, especially carbohydrate-rich ones, so labs often prefer a fasting morning sample. Hemolysis and delayed separation of the sample from the cells can raise the result falsely. Reports may show it as Fosfato.
Often read alongside: Calcium (total), PTH (intact), Vitamin D (25-OH), Creatinine, Magnesium