Although L-Carnitine in theory is "safe", according to the Natural Medicines Comprehensive Database (started in 1999 it's truly "comprehensive") L-Carnitine can
cause side effects such as seizures, stomach upset, heartburn, diarrhea, nausea, and vomiting... It can also cause a "fishy" odor to your breath, sweat and urine.
The database reports that it is effective
for increasing red blood cell count in people with serious kidney disease.
Only Possibly Effective
for preventing side effects for people on certain seizure meds, and possibly effective
for improving symptoms and complications of heart disease and heart failure, and possibly effective
for treating male infertility under certain circumstances.
They add that despite manufacturers'
claims, there is insufficient Evidence
that it helps fatigue, high cholesterol, circulation problems, attention deficit disorder, lyme disease and the list goes on and on.
P.S. Heart rate of 64 and BP of 125/66 is fine!
P.P.S. I personally would feel queasy about taking any of the myriad of supplements out there, no matter how innocuous they may seem, without at least informing my doc abut it.