Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Get emergency help now if you are bleeding heavily after birth, especially if the bleeding is pouring or rapidly soaking pads.
Also treat it as an emergency if you feel faint, confused, very weak, short of breath, clammy, or aware of a very fast heartbeat.
Call emergency services and, if possible, have someone stay with you.
Seek urgent same-day assessment if bleeding becomes heavier after it had been easing, you pass repeated large clots, or you develop fever, worsening pelvic pain, or unpleasant-smelling discharge.
These can be signs of secondary PPH or infection.
Arrange routine follow-up if fatigue, dizziness, headaches, breathlessness, or heart pounding are not improving.
You may need a blood test for anemia or a review of your iron treatment.
Routine follow-up is also appropriate if you want to understand the events of the birth, discuss emotional effects, or plan for a future pregnancy.
The article also says
Do not drive yourself if you feel faint or the bleeding is heavy.
Every sign above is quoted from the sofidex article on PPH. If you are not sure, err upward — it is always reasonable to be checked.