Africa 
China 
Japan 
MENA 
- New Animal Drug Application
- New Delhi metallo-beta-lactamase 1
- New York Heart Association Functional Classification
- New daily persistent headache
- Newborn hearing screening
- Newborn infant
- Newborn screening
- Newcastle disease virus
- Nexin
- Nexobrid
- Nexplanon
- Next generation sequencing
- Next-generation sequencing
- Nfix
- Niacin
- Nialamide
- Nibrin
- Nicardipine
- Nicastrin
- Nicergoline
- Nick translation
- Nickel
- Nickel allergy
- Nickel hydroxide
- Nickel oxide
- Nickel titanium rotary file
- Niclosamide
- Nicorandil
- Nicotiana
- Nicotiana tabacum
- Nicotianamine
- Nicotinamidase
- Nicotinamide
- Nicotinamide adenine dinucleotide phosphate
- Nicotinamide mononucleotide
- Nicotinamide phosphoribosyltransferase
- Nicotinamide riboside
- Nicotine
- Nicotine dependence
- Nicotine nasal spray
- Nicotine patches
- Nicotine poisoning
- Nicotine withdrawal
- Nicotinic acetylcholine receptors
- Nicotinic acid
- Nicotinic acid adenine dinucleotide phosphate
- Nicotinic agonists
- Nicotinic antagonists
- Nicotinic receptors
- Nictitating membrane
- Nidation
- Nidogen
- Nidogen-2
- Nidovirales
- Niemann-Pick disease
- Niemann-Pick disease type C
- Nifedipine
- Nifuroxazide
- Nifurtimox
- Nifurtimox-eflornithine combination treatment
- Nigella
- Nigella sativa
- Nigericin
- Nigerose
- Night blindness
- Night eating syndrome
- Night owls
- Night sweats
- Night terrors
- Nightmare disorder
- Nightmares
- Nijmegen breakage syndrome
- Nikethamide
- Nikkomycin
- Nikolsky's sign
- Nil per os
- Nile Blue
- Nile Red
- Nilotinib
- Nilutamide
- Nilvadipine
- Nimesulide
- Nimetazepam
- Nimodipine
- Nimorazole
- Nimotuzumab
- Nines
- Ninhydrin
- Nintedanib
- Niosomes
- Nipah virus
- Nipah virus infection
- Nipecotic acid
- Nipple
- Nipple adenoma
- Nipple discharge
- Nippostrongylus brasiliensis
- Niraparib
- Nirvanol
- Nisin
- Nisoldipine
- Nisoxetine
- Nissen fundoplication
- Nissl bodies
- Nissl substance
- Nitazoxanide
- Niter
- Nitinol
- Nitisinone
- Nitrate reductase
- Nitrate reduction
- Nitrates
- Nitrazine
- Nitrendipine
- Nitrene
- Nitrenium ion
- Nitric acid
- Nitric oxide
- Nitric oxide synthase
- Nitrides
- Nitriding
- Nitrification
- Nitrifying bacteria
- Nitrilase
- Nitrile
- Nitrile hydratase
- Nitriles
- Nitrite
- Nitrite reductase
- Nitrite test
- Nitro blue tetrazolium chloride
- Nitro group
- Nitroalkene
- Nitroarginine
- Nitrobenzene
- Nitrocellulose
- Nitrofuran
- Nitrofurantoin
- Nitrofurazone
- Nitrogen
- Nitrogen 13
- Nitrogen balance
- Nitrogen compounds
- Nitrogen cycle
- Nitrogen dioxide
- Nitrogen fixation
- Nitrogen metabolism
- Nitrogen monoxide
- Nitrogen mustard
- Nitrogen narcosis