Can someone please explain: what is the benefit of using high absorbent bed pads, if the bed is already covered with a mattress protector?

The pad goes on TOP on the bottom sheet, in care that isn't clear, not under it, and they're very thin. Every hospital uses them under their patients, too, even though the bed mattress is completely covered in plastic.

Fred, be sure and avoid bleach when washing reusable waterproof items. It destroys the waterproofing.

An advantage of good size chuxs is if you have a bed ridden person, you can use them to help turn and put a pillow behind

I understand the mattress protection. It’s easier than changing the entire bed. I never understood why some people wore two poise pads. That never made sense to me.

Lots of good explanations - guess I' ll get on to Amazon and order some. Thanks to all of you. Glad I found this site!

The disposable ones are called Chuxs. They come in two sizes, the smaller is blue and the larger is a peach color and thicker.

Rather than have to take the sheet and mattress cover off to wash each time the bed gets wet, which is several times a day but certainly each morning for us, the pads enable us to simply rotate and wash them. Since the waterproof mattress cover is the hardest to remove and wash we put one of the washable pads on top of the matress cover then the sheet, then another pad or two on top of the sheet. For a while we did this with several layers so all we had to do was take the sheet and everything on top off revealing a clean set but for some reason that seems to have stopped and we actually have a waterproof mattress case then a waterproof cover etc…but the general idea is not having to remake the entire bed every time it gets wet, just pull off the pads and put new ones on. We do then put white vinegar on the wet pads and let them soak in it before washing. We do all of this when she goes off to the bathroom in the morning, it takes her a while and not having to watch what is entailed just having it clean when she gets back is much easier on her emotionally.

Bottom line it saves you from having to change the sheets and mattress protector daily. Washing or throwing away(in the case of disposable ones)bed pads is much easier and can be done weekly(if you have enough)instead of having to wash daily all the bedding.
It really is a no brainer, and will cut down on your workload.

Depending on how wet the waterproof mattress protector gets sometimes that also has to be washed. Washing and drying a waterproof cover like that can take a LONG time as they really should not be put in the dryer. (at least I never did I figured it would break down the protective layer)
I also use the washable absorbent pad as a "draw sheet" and it also served as a spot on the bed that I could place soiled wipes, brief. then it could be folded with the soiled items in it so that kept the rest of the bed clean. A clean pad could be placed under my Husband as the other one was removed.
With the last few mattresses he had I could not use a waterproof mattress protector as the mattresses had an air flow to help prevent pressure sores. Waterproof covering over the entire bed would have prevented proper air flow and or movement of the inflatable tubing. For those mattresses a flat sheet was the only thing that went on the mattress and a washable or disposable pad over the flat sheet.
I have to tell you when he was in our large bed WITH a waterproof mattress pad AND pads he would still leak through and I found that I was changing the bedding a few times a week, including the waterproof mattress protector. So they do not always protect the way you would hope they would.

You're trying to protect the bedding (sheets, blankets) from urine...not the mattress.

Depending on your current workload, disposable bed pads can be used as well. I agree with cwillie , replacing a bed pad is easier than changing the entire bed.

Small leaks can be dealt with by changing the pad rather than having to strip the whole bed. Large leaks are contained so they don't overflow down the sides of the bed and/or into pillows and blankets. And it's much easier to swap out a bed pad in the middle of the night, especially if you layer one on top of the other.

The bed pads I bought were also larger and were invaluable in assisting me with turning and repositioning.