While it is possible to achieve sufficiently-high levels via transdermal gel or patches, it is typically more-difficult.
& for those on pills, which are typically the cheapest method on prescription, it's just not practical, even if you take the pills sublingually or buccally rather than orally.
As such, if your aim is pure feminisation or masculinisation, you will require a blocker of some kind if you still have hormone-producing gonads.
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