Get frequent leg cramps at night (calf) and they are so severe that the pain last for weeks and I cannot walk properly. Is it due to heart issues as I am diabetic/hypertensive? My urine is colorless even after drinking nothing. Why?

Cramps legs. This is not from the heart or arteries. It could be from leaky veins (venous insufficiency) or electrolyte imbalance. See a doctor or vein specialist.
See doctor. There are many possibilities for the cramping. The fact that you already have some serious medical issues. You should see a doctor for complete evaluation. Don’t second guess. See a doctor .