It can cause problems in some people by increasing someones iron to the point that the blood thickens, increasing the viscosity, or the resistance to flow. This will show up in a blood test as high hematocrit and hemoglobin. It can also be from being dehydrated. Therapeutic blood donations and staying hydrated is the common thing to do if your lab work shows high hematocrit and hemoglobin. That's why it is super important to stay on top of blood your work. If you have had high H/H then your period blood panel is good but it's a good idea to buy a H/H kit by mail and do them at home. They are only a few dollars and just give H/H results. That way you can monitor your H/H in between the scheduled blood tests.
There are risks TRT. That is why it's important to understand what your doing and get your blood checked.