You can Google the causes of high hemoglobin yourself. This covers it pretty well:
High hemoglobin count Causes - Mayo Clinic
IMO, your result isn't scary high. Double or triple over the laboratory top number, worry. I'd keep an eye on it in case it continues to trend up.
But bear in mind, laboratory values are just general guidelines, they take the average of readings from healthy individuals. That means there's always going to be people who are outside the norm. I'll give you a good example. My husband has had chronically low platelets for nearly ten years. VERY low. But no other symptoms (no bleeding problems, no healing problems, no bruising problems). However, one of the first things doctors think when they see a number like his - leukemia. The go-to test to ferret out the cause of low platelets being biopsy of liver or bone marrow, neither is as inconsequential a procedure as doctors like to let you think (in fact, I know a reasonably healthy person who coded during a liver biopsy). I have always gotten a copy of his bloodwork and have been keeping an eye on this myself so whenever his doctor starts squeaking about further testing I have to remind him to remind his doctor that he has numerous years of studies showing his platelets run low with no ill effect.
The fact is, if it was leukemia he would be dead by now, and he has no ill effects from his low platelets so this is his normal, leave it alone. Sometimes doctors cause more harm by poking around and testing stuff just because they're nosy instead of accepting that the human body is not one size fits all.