Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Call emergency services if paleness appears with chest pain, severe breathing difficulty, fainting that does not quickly resolve, confusion, cold and clammy skin, or major bleeding.
These symptoms can indicate serious blood loss or a problem with circulation.
Emergency assessment is also needed if a hand, foot, finger, or toe suddenly becomes pale, cold, very painful, weak, or numb.
This may mean that blood flow to the area is blocked.
And for anyone, someone who:
Seek same-day medical advice if new paleness occurs with worsening shortness of breath, repeated near-fainting, a very fast heartbeat, or unusual bleeding.
Vomiting blood, passing a large amount of blood, or passing black, sticky stools needs urgent assessment.
Iron tablets can also darken stools, but unexplained black, sticky stool should not be ignored.
Book a routine appointment if paleness persists, keeps returning, or comes with ongoing tiredness, headaches, reduced exercise tolerance, heavy periods, weight loss, or changes in bowel habits.
Children should be assessed if paleness persists or occurs with poor feeding, unusual tiredness, reduced activity, or slowed growth.
Every sign above is quoted from the sofidex article on Paleness. If you are not sure, err upward — it is always reasonable to be checked.