Caveat to any advice is there may be differences of opinion amongst the different schools of jurisprudence. Therefore, we advise people to refer to scholars of their choosing for their specific cases.
There is consensus however that injections, specifically subcutaneous and intramuscular, and transdermal preparations do not invalidate the fast as they offer no nutritional benefit, and nor are they entering the gastrointestinal system directly.
Hence, as opposed to other types of medication administration such as oral or nasal, TRT can be administered with the usual method, dose and timing. In addition, blood testing, either using capillary blood collection or intravenously also does not invalidate the fast. That said, it is advisable to wait for after Ramadan to avoid unnecessary weakness, If doing therapeutic philebotomy where 1-2 units is removed.
Sources:
- https://mcb.org.uk/wp-content/uploads/2021/03/MCB_Ramadan-Health-Factsheet-2021-1.pdf – Muslim Council of Britain – prepared by Mufti Mohammed Zubair Butt, Shariah Advisor to the Muslim Spiritual care provision in the NHS
- https://britishima.org/operation-vaccination/hub/statements/#FAST – British Islamic Medical Association
Mike Kocsis has an MBA with a focus on healthcare administration and is an entrepreneur and medical case manager for 
