Thank you for your medical query at AskTheDoctor.com
I understand your concern.
Yes, you can take supplements like Nutrigain or Ensure considering your BMI is significantly low.
You need to gain at least 10 more kgs to be healthier.
There are no side effects of this supplements. You also need to have a healthy diet containing more of fruits and green vegetables, adequate meat, e.t.c
Please meet a nutrition specialist who can take your dietary history and fix a diet for you, without which you will never gain weight in a healthy way. You need at least 1800-2200 calories per day and hence the diet has to be fixed accordingly.
Hope this was helpful,
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