can they take into the army, a guy who is being treated and is not...

According to Article 15 of the Law of Ukraine "On Military Obligation and Military Service", male citizens of Ukraine who are fit for this in terms of their health and who have reached the age of 18 before the day of being sent to military units are called up for military service. and older persons who have not reached the age of 27 and do not have the right to be exempted or deferred from conscription for military service.

During mobilization, all conscripted Ukrainians aged 18 to 60 can be called up for military service, if they do not have legal grounds for deferment or exclusion from military registration.

So, they can take a boy who has turned 19 years old into the army.

However, if a boy suffers from certain diseases, he may be deemed unfit for military service. The list of such diseases is defined in Appendix 1 to the Regulations on military medical examination in the Armed Forces of Ukraine, approved by the Order of the Minister of Defense of Ukraine dated August 14, 2008 No. 402.