Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
Go to an emergency department or call emergency services if dark urine occurs with very little urine, severe or worsening muscle pain, major swelling, profound weakness, fainting, confusion, persistent vomiting, or an irregular or racing heartbeat.
These features may indicate severe muscle breakdown, kidney injury, dehydration, or abnormal body salts.
Seek urgent same-day medical care for dark brown or red urine after exercise.
This may be myoglobin from muscle breakdown, even if the muscles no longer feel painful.
Arrange a routine medical appointment if you have repeated exercise-related muscle pain, cramps, or unusual fatigue, particularly if symptoms improve after briefly slowing down.
These symptoms have several possible causes and need proper assessment rather than self-diagnosis.
If you already have the condition, arrange follow-up when:
The article also says
While waiting for help, stop exercising.
Do not try to “work through” severe pain.
Every sign above is quoted from the sofidex article on Type V glycogen storage disease. If you are not sure, err upward — it is always reasonable to be checked.