What can cause high platelets and low calcium in labs?

Myriad of things. Sx. There are a myriad of things that can cause low calcium & high platelets. W/o knowing ur symptoms & medical history, it's next to impossible to interpret these results. High platelets can be a "stress" reaction to illness/infection, or a bone marrow prob. Low calcium can b from vitamin D deficiency or low sun exposure (Nordic genes). The most common cause is lab error. TTYD to clarify the results.
Highplatelets/lo ca. Recheck in 2-4 weeks. How high are platelets?How low is ca? Causes of hi platelets asplenia, myeloproliferative dx, CML, polycythemia, autoimmune disease, RA, Kawasaki, infection,nephritis/nephrotic (kidney)syndrome. Concern if > 750,000. Causes of low calcium include low protein, hypoparathyroidism, low Vit D , kidney disease. Check kidney/NSAID use, discuss with doc.
Context = everything. Let's consider: how "high" are your platelets, and how "low" is your calcium? Teeny differences are usually considered OK. If your doc is worried about the calcium, s/he may want to get an "ionized calcium" (more diagnostic). Regular calcium is usually bound to serum protein, so by itself is not meaningful. Re: platelets, same deal. What was rest of CBC? May want blood smear to see platelet shape .