Supplying adequate calcium and phosphorus in parenteral nutrition remains challenging because of:

• A. Limited solubility
• B. High cost
• C. Frequent precipitation
• D. Not necessary

Answer: (A)

Calcium and phosphorus must be delivered in parenteral nutrition as dissolved ions. Their tendency to form calcium phosphate leads to precipitation because the solubility of calcium phosphate is limited in PN solutions. When you try to meet daily Ca and P requirements in a single bag or line, high concentrations, unfavorable pH, or interactions with amino acids can push the solution to saturation and precipitation. This precipitation not only reduces how much you can deliver but can pose a risk if infused, so strategies focus on keeping Ca and P in solution—controlling the Ca:P ratio, adjusting pH, using citrate to enhance solubility, or delivering them in separate bags or lines. Thus, the main challenge is maintaining solubility; other factors like cost or the occasional precipitation observed are consequences rather than the root issue.