My mom is in the home hospice. They stopped all her medicine and last night her insulin too. Her health issues are diabetes, Alzheimer’s, COPD. How long can she survive without insulin?

I am so sorry that your mother needs hospice. That means she is in the end stage of one or more of her conditions.

Hospice almost always discontinues all medications that aren't providing current comfort care. Treating diabetes is generally intended to prevent complications down the road. That really isn't applicable when you are on hospice care. If Mom were eating normally or even close to a normal amount, Hospice would probably give her insulin to help metabolize that food. But giving insulin when the patient is not eating would cause low blood sugar, and that is more immediately risky than high blood sugar.

Of course you don't want her to suffer! And that is the purpose of hospice care. In my experience the hospice staff is very good about answering questions and explaining what they are doing and why. Ask the nurse and/or the social worker what your mother's current condition is, and why they are taking the measures they are. I think you will feel much more comfortable with explanations from them.

This is a very hard experience to go through with a loved one. Continue to show your love; that is really about all you can do, but it is an extremely important thing to do!

If her blood sugar is within normal limits she may not need insulin as she isn’t eating anything or very little by mouth that would cause her blood sugar to be elevated. Insulin should not be given if her blood sugar is low.

Do you know if someone is checking her blood sugar with a glucometer and if so, what are her blood sugar levels?

She may be treated with sliding scale insulin according to her blood sugar at that time. Or she may be on a once daily dose. 

Hard to tell without a little history, but I am guessing she is on sliding scale regular (humalog, novolog) fast acting insulin coverage according to her blood sugars at the time. 

Usually the doctors will specify how much fast acting insulin should be given for a blood sugar range, thus it’s called “sliding scale” coverage.