Had kinda the opposite happen to me fell out of breathe and increased heart rate with minor exertion, felt light headed.
Family: you're out of shape
Google: anemia
Me: anemia, EZPZ just see the doc and get some iron pills, right as rain
Doctor: Leukemia
The emergency room doctor said my hemoglobin was "impressively low" it was at 3.9 g/dL