Cholesterol too low?

My age is 77, male.  Cardiac history: heart attack (mild) 1981; heart bypass 1992; valve replacement 2001, redid bypasses.  I was on 40mg Lipitor and 500mg no-flush niacin for a number of years with moderate sucess.  I subscribe to the Cleveland Clinic Heart Newsletter.  In the July 2007 issue there was suggestion that 1,500mg niacin was a good statin supplement.  Starting in July 2007 I followed this suggestion, taking 1,500mg slow-release niacin with the Lipitor.  I have biannual blood tests.  The past three tests, 7-07, 12-07, and 6-08 showed my cholesterol to be 149, 85, and 57mg.  LDL 65, 26, and 16mg.  Triglycerides 183, 29, and 36mg.  HDL 47, 53, and 34mg.  These were dramatic improvements, except for the HDL.  I am advised the 'good' cholesterol range is 50-200mg.  If mine goes below 50mg in the next test do I have a problem?  After the last test, doctor reduced my Lipitor prescription from 40 to 20mg.  On my own decision I have now reduced the niacin from 1,500 to 1,000mg.  I guess my question then is, should I be concerned if my cholesterol drops below 50mg?  And I wonder about the HDL being 34mg in the last test.  For so long as I can remember my HDL has always been above 40mg.  Could the 34mg reading be the result of the substantial LDL decrease?  For the past 20+ years my triglycerides have been in the 160-200mg range.  The sudden decrease to 29 and 36mg seems strange, (to me,).

[Momto3]

You pose a very interesting question.  I remember my cardiologist telling me (in the 1980's) that people with low cholesterol were at high risk for stroke : (  Since that time, it seems that research suggests lowers numbers are OK.

Here is an applicable article that I though you might find interesting:

http://209.85.215.104/search?q=cache:uWv0GKyW0nYJ:www.medicineonline.com/news/10/6519/Cholesterol-Levels-Can-t-Be-Too-Low.html+can+cholesterol+be+too+low+and+cleveland+clinic&hl=en&ct=clnk&cd=5&gl=us&client=firefox-a

[MysteryChemist]

I take Niaspan which is an extended release form of niacin.  Niaspan will decrease your LDL and triglycerides and increase your HDL.

I would not change your niacin dose w/o talking to your doctor about it. Decreasing the dosage could decrease your HDL.

I was taking 1500 mg of Niaspan at one point for about 7 months My HDL was around 42-44 for 3 measurements. It then drop to 32. My cardiologist immediately bumped my Nispan dosage to 2000 mg and my HDL went to 50 a year later.  My triglycerides have drop  from 123 to 39 since I have been on Niapsan.

Again, I would not change the niacin dosage, either up or down, w/o talking to the doctor about it.

[Eroteme1]

Agree, thank you, will resume the 1,500mg.  I could also have said I have not taken the 1,500 niacin in a gulp, I have taken three 500mg tablets morning, noon, and evening.  This I suppose may or may not have had an effect on the mostly favorable results. I errored at the beginning, taking the 1,500mg suggest from th CHC without telling my doctor.  As it came to be, he was amazed at the results, so I guess no harm was done.