Is it possible to have high b12 in blood tests but still be deficient? my levels are 1800 (no supplements so don't really understand that) but feel like l have deficiency symptoms?

There is likely a different condition still to be diagnosed that may have overlap symptoms with vit B12 deficiency. A hematologist’ s input will be needed.

Functional deficiency of B12 will result in elevation of methyl malonic acid in urine and your doctor can test for that. "feel like l have deficiency symptoms" is not a reliable sign. With your B12 level you are not deficient. Visit this site for info: https://myhealth.ucsd.edu/Search/167,methylmalonic_acid_urine