I start taking my meds on November 2nd (Videx, Epivir, Stocrin) and my viral load is undetectable. But, last week, I forgot for the first time to take my meds for one day. So now I would like to know how big are the chances that I have become resistant to my treatment?

There is a real but small risk of resistance any time a scheduled dose is missed. However, once you have achieved an undetectable viral load, the risk of a single missed dose is less than it is during the first 6 months of treatment when your viral load is falling, but still detectable. It is very likely that you will be fine if you simply resumed your same regimen after the single lapse.

On the other hand, I suggest that you take some time and energy to make sure that you don't forget to take your medications again, to ensure that you don't expose yourself to that small risk of resistance.

There is currently a clinical trial of patients who, once undetectable, take their medications five days per week, and then take no drugs for two days on the weekends, compared to another group who take their medications every day. To date, the treatment outcomes in the two groups are similar, though these data have yet to be published, and so caution should be used before deciding to try this yourself.

I suggest that you talk to your doctor about the lapse in adherence, your concerns, and that you and he or she repeat your viral load to look for the possibility of early treatment failure and drug resistance. The odds are in your favor that it has not occurred due to this single instance.