How much can you lower your alcohol tolerance and how does that effect a potential hangover?

they say not drinking for 3-4 weeks lowers your alcohol tolerance by a large margin. say if you drink 7 drinks before getting drunk today and you have a hangover tomorrow, then you go 3 weeks straight without drinking at all. when you drink again in 3 weeks, will it only take 5 drinks to get drunk and consequently hungover, or will it take 5 drinks to get drunk, but still 7 to get a hangover?