White lips after exercise may be caused by anaemia, but it may also be caused by other factors, such as transient factors, localised skin ischaemia after strenuous exercise leading to white colour. If the patient recovers from the symptoms after rest, there is no need to be particularly concerned.
It may also be caused by low blood sugar. If accompanied by significant dizziness and nausea, patients are advised to go to the hospital to measure their blood sugar to clarify whether it is hypoglycaemia and to deal with it promptly.