Thanks for your response. I currently take 2000 IU's of vitamin D per day and still my phosphorus is going down. My calcium levels are normal: 9.5 - 10.0. I do not drink alcohol nor do I take antacids; however, I will bring the other issues you mentioned up with my doctor. Thanks again.
Low serum phosphorus is usually caused from vitamin D deficiency, malabsorption; medications binding phosphate, such as antacids, steroids, insulin, and epinephrine; large consummation of alcohol; and certain disease states, such as, renal failure, hyperparathyroidism, and DKA. Phosphorus is very abundant in our food sources especially in dairy products and meats. An increase in phosphorus foods will increase your Vitamin D and calcium levels, too. If your levels do not increase from increase of foods, then suggest having your MD check medical reasons as examples above.