Palestine Press Agency has an article Gaza hospitals that do not have basic medical supplies, like pain relief medicines and even gauze.
Families of patients have to go to pharmacies to buy the medicines - of which the pharmacies have where there are plenty - and then give them to the nurses at the hospitals to administer.
What is interesting is how the medicines in the pharmacies are labeled. They say things like "In support of the Palestinian people" or "in support of charity X." In other words, medicines that are meant to be given to the hospitals for free are being diverted and being sold to pharmacies instead, for what is presumably a tidy profit for the thieves.
Israel does not limit the shipment of medicine and medical supplies at all.
The PA is responsible for coordinating shipments of medicine to Gaza, and they have only been sending roughky half of what was needed, thus creating a black market for the supplies.
Although this article did not explicitly blame Hamas, we have seen in the past that Hamas has confiscated aid meant to be distributed for free and diverted it to Hamas-run hospitals and clinics, or to the black market.