When parent starts becoming forgetful and mixes up meds etc. is it okay to leave them for short periods? Can I trust her not to be unsafe?

"Just old age". Hmm I know 90+ yr olds that are very sharp with no memory problems.

Family, especially close family like you often notice memory & other cognitive changes years before a Doctor will. (To their defence a Dr may only see the patient, paying attention well, in a 10 min consult).

Many times a general practicioner has ruled out dementia but a thorough neuro exam will highlight exactly what level each skill is at (short term memory, longer term, reasoning, spatial, judgement, maths, word finding, language & more).

Is it worth doing all that now? To get a baseline? I can't answer that.

What I would do is invesrigate. Arrange a thorough medical to rule out all other reasons for these symptoms. UTI is common or some other infection. Also vitamin deficiency, reduction in kidney function or cardiovascular problems.

Trust your gut instinct. Keep looking for answers.

If you have already quit you job to supervise/assist full-time, this means your Mom is no longer independent & something is amiss.

"Just" is a very dangerous word. 'Old age' issues at 77 sounds suspicious to me. While being a bit forgetful is a normal part of aging, being 'disoriented' & mixing up meds is not. If you feel uncomfortable leaving her alone to go out and run a few errands, what does that tell you? Asking us if it's okay TO leave her alone in the house for a short while is a very telling question, in my opinion. YOUR hunches and instincts are way better than some doctor giving you the 'all clear' on your mom when he doesn't even know her! What tests has he actually given her? When I speak to my mother's NP, I always tell her that she doesn't really KNOW my mother b/c she only sees her for 10 minutes once a week! It takes YEARS to get to know someone and even then, only the scientific tests tell the real story, you know? Did she have a MoCa exam? What was her score out of 30?

Anyway, if you don't feel comfortable leaving mom alone, then don't. There's nothing better than a daughter's instinct, that's what I've learned over the years! Get a camera or two to put around the house or only leave her if she's having a good day, like Grandma1954 suggested. It's not realistic to NEVER be able to leave the house, so look into getting an aide to come in a few days a week for a few hours; get mom used to having someone else to care for her so you're not tied down 24/7 and so she's not fully against having outside help. We see that problem here all the time. Get that set up (using HER $$$) asap, that's my suggestion. And then run your errands and get your alone time while the CG is at the house.

Wishing you the best of luck with all you have on your plate.

Do you have cameras in the house so if you go out you can monitor what she is doing?
If not it might be a good idea to get a few.
If mom is having a good day go run your errands but if it happens to be a day where she seems particularly confused I would stick to home. Or if mom is able take her with you to the store or to run the errands you have to do. She might enjoy getting out for a while.
I also think the doctor did a great disservice in giving his "diagnosis". I think it warrants a visit to a Neurologist or a Neuropsychologist for a thorough evaluation.

I also do not like the feeling that her doc may have kind of given her the brush off. If she's forgetful and mixed up her meds, then I think there is something going on besides "old age". Everyone ages differently and it's not, IMHO, normal to be that confused at 77. My mom is a little older than that and we're doing testing, etc. to try to figure out if there is a reason that she's confused and having short term memory issues. Don't give up. Can you look at her records to see exactly what kind of tests have been run on her? Did they do the memory test and if so what were the results? Have they done blood work? They tested my mom's b12 and thyroid levels cuz that can lead to confusion. Also some meds can contribute so we weaned off a few and changed one. Didn't help but it COULD have.

Does your mom do any dangerous things like use the stove? Leave the water running? Does she ever leave the house and wander? If she's not been showing any potentially dangerous behaviors and you have no reason to anticipate her doing things like any moment, then it could be deemed reasonable to leave her alone for short periods of time. My mom's a bit confused but I leave her alone to run errands, go on a visit, but I really don't feel she's a danger. Yet. Just do an honest assessment.

Your profile says your mom is 77 years old. How did her doc "rule out" ALZ (which comes under the umbrella of dementia, of which there are many types)? If the doc is the one who said it's "just old age setting in" to you without discounting other medical issues that can cause confusion (like UTI, thyroid issues, diabetes, high blood pressure, brain tumor) then I would take her to another doctor.

Did this doctor give her an actual cognitive/memory test (the one where she has to remember 3 words after 10 minutes and also draw a clock face and put the hands correctly when they tell you a time)? Did your mom have her exam without you being in the room? Because she may not be remembering what the doc actually said to her, or she is hiding something from you about her health.

I have an aunt who is 102 yrs old. I pay for her subscription to the Wall Street Journal, which she reads every day. My own mom when she was 77 could run mental circles around most people her age and younger. Confusion in old age is not really "normal" but is a sign of something else. One of those "something else" things is cognitive decline aka dementia. If your mom doesn't have an accurate diagnosis you won't be able to be her best advocate because you won't really know what you're dealing with and what treatments or therapies would help her the most.

You also might want to watch some Teepa Snow videos on YouTube. She is an expert on dementia and caregiving. She goes through what dementia is, how it creates the changes in our LOs, what those charges are (stages) and how to better interact with our LOs to make everyday life with them more productive and peaceful.