(to be clear: not a doctor)

the "daily" recommended doses are for a single day. If you are taking it daily you need to at least halve the recommended dose. I wouldn't have said a week was a problem but... yeah. Tylenol is dangerous.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4913076/

Specifically this study referenced: https://jamanetwork.com/journals/jama/fullarticle/211014

> One study reported that ingestion of the recommended maximum amount of 4000 mg of APAP for 2 weeks resulted in the asymptomatic elevation of alanine transaminase, up to three times normal, in 40% of patients.19 These transaminase elevations did not amount to any clinical significance, and after the APAP was discontinued the transaminase levels returned to normal.19 Yet, while asymptomatic, chronically elevated aminotransferases may be of concern to healthcare providers, leading to further costly diagnostic studies or changes/restrictions in necessary medications

If anything the summary in that review is underselling it. Average was 2.78x baseline (3x is considered clinically significant) and 20% of the population was over 5x the peak (so, 20% had clinically significant elevations from the study). By peak levels, around 27% of the population saw peak levels of 8x baseline. So basically, even the "average" participant was almost to the threshold of clinical significance just from this study (at the recommended daily dose) and a cohort of around 20-25% will see clinically-significant warning signs at the recommended dosage, even among healthy patients. And risk factors significantly increase that.

That's basically a "liver stressor" enzyme, even if it's not killing the patients over the course of the study, it's not a good thing. That's your body's warning signal that it's stressed. And generally that's an uncontroversial finding I think, everyone agrees tylenol is a liver stressor, but they just have various thresholds of the acceptable risk. Would I do it daily? No.

And in med-speak, that's what they're saying here too. Use with caution, don't go above the recommended dosage in acute situations and use caution with chronic dosing. https://pubmed.ncbi.nlm.nih.gov/11847957/

Anyway, the rule of thumb I always heard is that half of the "daily" dose appears to be more appropriate for chronic daily usage. I am not a doctor and you can do whatever you want, but that is personally what I would hold to. Going less, or picking a different FDA-approved alternative like ibuprofen or aspirin, is always a perfectly acceptable choice.

That number appears to be reasonably supportable too. Instead of "half of our patients were over triple their baseline ALT level" this study found that 50% of the daily doage, chronically over 12 weeks, gets you to a 20% average increase in ALT levels. It's never not going to be a liver stressor and if you have other risk factors then you should probably stay away entirely (I think that's just good advice in general) but 20% increase in ALT after 12 weeks is a hell of a lot better than tripling your ALT in 2 weeks. But even then, during a 12-week study of 94 healthy adult patients, at half the recommended dose, they still had to withdraw one participant due to hepatotoxicity. https://pubmed.ncbi.nlm.nih.gov/25899926/

(as far as risk factors, see the first link above for a good review, aggravating factors for hepatoxicity can include things like non-alcoholic fatty liver or nutritional deficiency. Which basically describes an overweight computer-toucher with a poor diet to a tee.)