Very high triglycerides can be caused by poor diet and not enough exercise. You may also have inherited very high triglycerides from a parent. Your doctor will tell you how to manage your triglycerides. If your weight is higher than what is considered healthy, losing even 5 pounds may help lower your triglycerides.
WORD likes it un-hyphenated but I don't. Long-term should be hyphenated but longtime should not be hyphenated, at least until a few more decades pass and the grammatical rules for the use of hyphens either relax or fade away. Here is part of an erudite commentary on this subject:
When a compound adjective follows a noun, a hyphen is usually not necessary. Example: The apartment is off campus. However, some established compound adjectives are always hyphenated. Double-check with a dictionary or online.