25mg - allergy relief, anti-nauseant.
50mg-150mg - you'll get tired and feel like a zombie. This is the dose DPH is used at for sleeping pills.
175mg-300mg - you'll be really tired and your memory may lapse, it will be hard to concentrate or talk, limbs get very heavy, mucous membranes start to get dry
300mg-600mg - you might see things that are not, in fact, there. delerium may set in at higher doses.
600mg-1200mg - delerium, you are unable to distinguish the drug induced hallucinations from reality and may end up doing really horribly bad stuff like stripping naked and running into traffic. few people remember the experience entirely at this level. quite a few end up arrested or in the hospital.
1200mg+ - risk of death, seizures etc