There are some instances where a dermal puncture is prohibited or not recommended.
As a general rule, a dermal puncture, or a venipuncture, should not be performed on the side affected by a mastectomy. The body's ability to fight infection is compromised if lymph nodes were removed. A physician's permission must be obtained before performing a blood collection procedure on the same side as a mastectomy.
Dermal punctures should not be performed on previously punctured sites or swollen sites. Excess tissue fluid may contaminate the specimen.
If the patient is dehydrated or has poor circulation, it may be impossible to get a quality specimen.
Fingerstick on a newborn or young infant
Dermal punctures must never be performed on the fingers of a newborn or very young infant (usually defined as under 12-months-old). There is very little distance between the skin and the bone. Therefore, the bone could be easily pierced during the puncture, causing injury to the bone, infection, or gangrene.