Mom has started sleeping 15-18 hrs a day and greatly diminished appetite. Should I be concerned?

It is possible, she is close to the end. Call hospice and see what they think. They will send a nurse out to qualify her, and you can talk to her. My Dad did this close to the end. My prayers are with you.

I agree freqflyer. Get her checked out for a UTI - NOW! If her urine output smells bad and/or is dark-colored looking - she may have a UTI. And if it's a UTI and doesn't get addressed right away, the bacteria could enter her bloodstream and then boom, she can become septic (develop a severe blood infection). If it's not a UTI, then tell your mother's doctor that this set of symptoms is unusual for her and has happened only recently and that you're very concerned because this not your mother's norm. My mother has severe urinary incontinence due to both kidney disease and to sphincter muscle and pelvic floor dysfunction. My mother's urinary output is bad all day long - but it's much, much worse overnight to the point that I have to include a super plus booster pad with her XL adult diaper. Her overnight urine output is 2.2 liters - that's a little over two full 32oz of Gatorade; imagine having to pee this out. She won't tolerate a catheter, though she really needs one. Our brains produce a hormone (anti-diuretic hormone) that is released at night and basically attaches to the kidneys, allow us to sleep all night long. This is why when we wake-up we have the morning pee. For my mother this "attachment" site is no longer working due to years of medication use for another medical condition.

Robyn, just an idea, have your Mom tested for a urinary tract infection as that can cause unusual behaviors in elders.

Are you checking her blood sugar? High levels can make you lethargic. What about her meds for arthritis. Sometimes long time usage can start to cause problems. That happened with my granddad. I would discuss with her doctor and have a full makeup of labs. Try to rule out infections, depression, blood sugar, etc.

Does she have dementia? Why is she incontinent? Does he really not have the energy or does not have the ability to control it?

Probably two-three months ago. All these recent scenarios have presented themselves in the last month. No new prescriptions.
Thank you so much for responding to quickly.

Robyn, when was the last time your Mom had a physical with her primary doctor? Your Mom is still too young to be sleeping so much, thus there has to be a medical reason. Has she changed any of her prescriptions? Sometimes new prescriptions will have a sleepy side effect.