MIL is in a nursing home, they want to give 20 residents intravenous hydration. Is this normal? She is in good health.

As an RN, this is one area I have to address with my clients. As much as possible, we should use functioning organs - namely digestive tract - to address issues of fluid balance and nutrition.
Ask for evidence of dehydration and malnutrition.
If she is voiding (peeing) every 3-4 hours while awake, she most likely is getting enough fluids. I would prefer to have orders to offer drinks every 3-4 hours over IV therapy for hydration (also less risk of infection).
If she can eat without impairment, she should be given 3 meals a day in her facility. If she doesn't eat much, she should be offered high caloric and nutrient dense snacks and drinks between meals (all those food bars and supplement drinks).
If they are worried about not getting her RDA of vitamins, minerals... she should be getting a multivitamin daily.
If she has problems with eating - choking risk or swallowing problems - and fluids and nutrition are a problems, IV therapy is not the recommended treatment. IV fluids for nutritional purposes carry higher risks than other IV therapy and require dedicated IV access. Most clients that I had with this type of problem with in a hospital. She would need a feeding tube placed into her stomach permanently. Ideally, she could then be given tube feeding that will provide all the nutrition and fluids she needs.

I would not approve it.

Tell Nursing Supervisor you need to approve anything given to her. Tell them to give Ensure or Boost in the flavor of choice! Hugs 🤗

You can bet the facility dr has ordered this. Money maker to boost the profits and probably easy to push through Medicare and Medicaid billing when they have used it as a blanket procedure like that.

Call her personal dr and see get his opinion

This is an infusion of vitamins/minerals. Is this being ordered by a legitimate physician? By that I mean one employed outside of the LTC facility?

I would ask why they feel you Mom needs this. Then I would call her PCP even if she is using the facilities doctor to see what he/she feels.

Not snake oil! I get this at my legit doctor. Magnesium and B complex. Treatment is for Fibromyalgia and ME/CFS. It helps with pain and fatigue and I have been able to cut back on pain meds!

Some people are skeptical of traditional medicine and prefer these alternative treatments, sometimes because of religious beliefs.

So they mix up all sorts of tinctures on their own as well.

Is this Meyer’s cocktail FDA approved?

I have had several Myers Drips over the years. I cannot take Magnesium orally, it triggers my IBS-D, but Magnesium is a necessary mineral. About 4 times a year I gets a Myers drip to boost my magnesium, B12 is added to it, any other vitamins are just a bonus.

For someone like me who has very few options to take Magnesium it is very beneficial.

The volume of fluid in the drip is not great, so unless they are adding the vitamins to 500 ml to 1 L, it is not going to be very hydrating. Also should not cost more than $100 per treatment, likely less.

I’d be suspicious at best. My mother spent four years in a NH, never saw or heard of it. Just looked it up and didn’t think a lot of what I saw

I'd ask the medical staff what the medical diagnosis is for your MIL and what this therapy is supposed to accomplish. If they say it's just for nutrition and if the resident doesn't want it, it would be considered "force feeding", which they can't do.

I found this on Wikipedia
"Myers' cocktail is an intravenous (IV) vitamin therapy that lacks sufficient scientific evidence to support its use as a medical treatment.[1] The term, Myers' cocktail, is included in Quackwatch's index of questionable treatments.[2]Medical experts warn that intravenous vitamins, such as the Myers' cocktail, do not have any benefits and should be considered modern-day snake oil"