What may be the cause for a b12 of 1003 and an aptt level of 35. i am not on any meds for blood thinning?

Supplements?: B12 is minimally increased-diet or supplement can do; not a problem. Ptt slightly up can be due to diet: dark green leafy veg sources and/or supplement. (assuming general good health).

Maybe nothing.: Elevated B12 levels usually are of no significance. The usual cause in a diet high in b12. A pathologic reason is rare, and would typically be much higher. The PTT of 35 seconds is borderline high, and might still be normal, or could be indicative of a mild inherited or acquired bleeding disorder. If the PTT was done to evaluate bruising or bleeding, further studies would be in order.