Short answer: Glucagon is for severe low blood sugar: a low so deep the person cannot treat it by eating or drinking, such as when they have passed out or cannot swallow. The NIDDK calls it the best way to treat a severe low. The Baqsimi and Gvoke labels say to give the dose, call for emergency help right away, give a second dose after 15 minutes if there is no response, and give food once the person can swallow.
The NIDDK says that for many people with diabetes, low blood glucose means a reading below 70 mg/dL. Mild to moderate lows can bring shakiness, hunger, tiredness, dizziness, confusion or irritability, a fast or uneven heartbeat and a headache. For those, it describes eating or drinking 15 to 20 grams of glucose or carbohydrate, checking again after 15 minutes and repeating until back in range.
A severe low is one so low "you can't treat it yourself." The NIDDK says it can cause passing out, coma or death, and that each year about 2 in 100 US adults with diabetes who take insulin or certain other diabetes medicines have one. For this, it says glucagon "is the best way to treat severely low blood glucose."
Both labels are for severe hypoglycemia in people with diabetes: Baqsimi from age 1, Gvoke from age 2. Their steps line up:
The Gvoke instructions add that a low may happen again after the injection, that the prescriber should hear about every severe low, and that the diabetes medicines may need to change. MedlinePlus says an unconscious person will usually wake within 15 minutes.
Glucagon works by making the liver release stored sugar (glycogen). Both labels (section 5.4) say it may not work when those stores are low, as in starvation, adrenal insufficiency or long-lasting low blood sugar. The Baqsimi label says people in these states should be treated with glucose instead.
The labels also rule out glucagon in people with pheochromocytoma or insulinoma, two rare tumors, and in anyone allergic to it. The Baqsimi label notes that people on beta-blockers may have a brief rise in pulse and blood pressure, and that in people taking indomethacin glucagon may lose its ability to raise blood sugar.
Because the person having the low cannot give the dose, the NIDDK suggests talking with the care team about when and how to use glucagon, checking the expiration date, teaching family, friends and coworkers how to give it and to call 911 afterward, and wearing a medical ID.
Dose Track can hold a glucagon device in inventory with its expiration date, and the glucagon storage page covers how each product is kept. The Baqsimi and Gvoke side-effect pages cover each product.
Read more on Dose Track: Baqsimi side effects · Gvoke dosing · How to store glucagon · Hypoglycemia (low blood sugar)