Drink lots of palmagranet juice. I mean 2 gallons in the 2 days before the test.
take niacin every day. If you feel a heat flush after taking it, thats good.
I agree with @jackm
Fudging the test results isn’t like faking a drug test, for example. This is your health and life. A lifestyle change is needed to have good cholesterol.
I assume this is for life insurance. Stress will mess up your numbers, so don’t worry about the results. @filmfann has some good suggestions. A good flush can come from about 1000 mg of niacin daily, but can bring your numbers in quite a bit in about a month. After that, it can really dry your skin, so I’d stop the niacin after the test.