Kapalbhati is a powerful yoga breathing technique that can be very invigorating, but it can also be challenging for some people, particularly if they are not used to it or if they have certain medical conditions. If you are feeling weak after practicing kapalbhati for 4 minutes, it may be best to stop and take a break. You should also consult with your doctor or a qualified yoga teacher to see if kapalbhati is appropriate for you given your haemoglobin level and any other health concerns you may have.
If you have a low haemoglobin level, you may need to focus on dietary and lifestyle changes to boost your iron levels. Eating more iron-rich foods, such as red meat, leafy greens, and dried fruits, and avoiding foods that inhibit iron absorption, such as tea and coffee, can help. Also, make sure you are getting enough rest and exercise, and avoid alcohol and smoking.
Additionally, other gentle pranayama techniques like Anulom Vilom or Bhramari may be more appropriate for you to practice in your current condition.
