As you've gathered, AST & ALT represent your liver function along with a few other tests grouped similarly. The upper limit of normal (ULN) varies depending upon the laboratory equipment used. In general, 30-50 is the high end. However, to put things into perspective, we typically won't bat an eyelash unless your numbers exceed 3x ULN or 90-150 depending upon lab test/equipment. Even then, we're allowed to monitor closely until you reach 10x ULN before asking you to stop the offending medication.
Other causes may includealcohol consumption, acetaminophen (Tylenol) use (which is found ubiquitously in combination w/many other over-the-counter medications), and fatty liver (due to obesity or being overweight). Medications are a frequent offender leading to an increase in liver function tests. Statins (cholesterol lowering meds) are the most well know for this side effect.
Of course, if someone doesn't drink alcohol, doesn't take acetaminophen, doesn't take a statin or other liver irritant, and isn't overweight/obese, yet has an increase in his/her liver function test(s), then it's imperative that we look for infections as a cause, eg hepatitis A, B, C, etc. HepA is food borne. Hep B & C are linked to sex and needle use/sharing, eg illicit intravenous drug use and tattoo parlors of ill repute (modern clean licensed facilities that don't re-use sterile disposable needles are exempt from this sweeping generality).
Picking up hepatitis from blood transfusions is rare these days, at least in the industrialized world given the testing & screening the donors undergo prior to being allowed to donate. Hope this helps. Chat with your family physician about your results and why the test was ordered as well as the plan to figure out what's going on. Good luck!
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