For people who already have heart disease, aiming to get their 'bad' cholesterol (LDL) below 55 mg/dL cuts their risk of serious heart problems by about one-third over three years compared to aiming for below 70 mg/dL — and it doesn’t seem to cause more side effects.

If you've had heart problems before, aiming to get your 'bad' cholesterol really low—below 55—cuts your risk of another heart issue by about a third compared to keeping it just under 70.

If you have heart disease from clogged arteries, getting your bad cholesterol down to around 56 mg/dL instead of 66 mg/dL can cut your risk of heart attacks or strokes by about a third over three years. For every 32 people treated this way, one person avoids a major heart problem.

For people with heart disease from clogged arteries, getting their bad cholesterol down to around 56 doesn’t cause more serious side effects than staying at 66, and it’s safe to keep it that low for at least three years.

When you have too much 'bad' cholesterol (LDL) in your blood, it sticks to the walls of your arteries and builds up like gunk, making them narrow and stiff — which raises your chance of having a heart attack or stroke.

Even if your heart looks healthy and you have no major risk factors, higher 'bad' cholesterol (LDL) — even when it's considered 'normal' — is linked to more hidden artery buildup. For every 10-point rise in LDL, the odds go up by about 15%.