The old fatal risk came from injecting into muscle. Modern subcutaneous-only technique with ultrasound has changed the numbers dramatically.
Fat injected into or below the gluteal muscle can enter large veins and travel to the lungs — a fat embolism. This mechanism accounted for the mortality statistics that made BBL notorious a decade ago.
International guidelines now restrict injection to the subcutaneous plane above the muscle, with the cannula angled away from deep vessels. Many surgeons, including ours, use ultrasound guidance to confirm the plane in real time.
Do you inject above the muscle only? Do you use ultrasound guidance? What volume per side do you consider safe? A surgeon who cannot answer these three questions clearly is not the one to do your BBL.
There is a ceiling to how much fat survives per side, typically 60–70% of what is grafted. Requests for extreme volume in one session are exactly where safety and result both deteriorate.
Safety depends on the surgeon's technique and the facility, not the country. Ask about plane, ultrasound and hospital ICU availability wherever you go.