Postural hypotension could be the reason. When you suddenly stand up from sitting position, all the blood will be pooled in legs and it takes few seconds to come to heart and reach brain. During this fraction of seconds you may feel lightheadedness.
This is more in people with low Hb. As you already have low Hb, that could be one reason.
Also you might be taking less water which is why you have yellow urine, also a
kidney stone as well. Good hydration is mandatory for you.
Other issues that you have is high BMI, low Hb, low
B12 and low
vitamin D which needs personalized treatment and lifestyle changes
Next Steps
feel free to consult me on practo for further evaluation and management
Health Tips
have you ever checked your BP.. sometimes high BP can also cause dizziness