You have not mentioned whether for a boy or girl as there is a difference. The average weight for a 20 month boy is 11.4kg and for girls 10.8kg. Weights below 10.5kg for boys and 9.9kg for girls would be considered to be underweight.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.