The American Kennel Club recommends brushing your Pom's coat twice a week to keep it in good shape. If you brush it more often, or have it trimmed to the undercoat, you run the risk of causing excess hair loss due to overgrooming. Shaving or cutting a Pom's fur short might seem like a good idea at the time, but you run the risk that it will never grow back with the same fullness.
Of course, any dog is going to shed, and double-coated dogs such as the Pomeranian tend to shed a lot. Twice a year your Pom will "blow his coat," meaning the thick undercoat is shed over several weeks. This happens more in climates with severe seasonal temperature shifts. An indoor dog without these climate cues often will shed equally as much year-round.
Pomeranians go through a stage in the first year of life called puppy uglies, when their fluffy puppy coat is shed. Eventually their adult fur grows in, but first they go through an awkward stage of having thin, wispy hair. Typically this will last for half a year, from the time they're 4 months old until 10 months.
Alopecia X is hair loss with no known cause, and it's one of the few health issues that can plague Pomeranians. Vets also call this adult onset growth hormone deficiency, while breeders often dub it black skin disease. It's also referred to a hair cycle arrest or coat cycle arrest. This abnormal hair loss can occur when the dog is anywhere between 1 and 10 years old, and may happen after the puppy ugly stage instead of the adult coat growing in. It sometimes involves his skin pigment changing color as well. Other than that, there are no symptoms that pinpoint the condition.
Hair loss can also go hand in hand with depression, changes in eating and drinking habits or liver or kidney problems. If you suspect any health issues or notice a change in your Pom's behavior, it's important to have him looked at by a vet.