Different labs can absolutely yield different results - especially the quality of equipment used and the technical skill of the lab tech. But for TGs nearly doubling, I'd suspect a dietary influence, not labwork - when my TGs came back staggeringly high last year I learned that eating something like sweet white corn the night before a blood draw can artificially drive up TGs. As per time of day for blood draw, the body and organs work on various 24 hr cycles, so it may impact some numbers - best to keep on a schedule, get it drawn around the same time of day for each test so you can rule out that effect.