According to Medicover Hospitals, black or reddish-brown spots on your nails can signal high cholesterol levels.
“The condition is caused by small, damaged blood vessels under the nail,” explains the health site.
The black or reddish-brown spots have the following distinguishing characteristics:
Do not change appearance when you apply pressure to the nail
Appear in one or more places under the nail.
As Medicover Hospitals explains, an accumulation of cholesterol in the blood vessels of the nails can cause this damage.
However, in most cases, you can only find out if you have it from a blood test.