N
The lowest point. For example, a person's nadir CD4 count is the person's lowest CD4 count.
See Related Term(s): CD4 Count
National Cancer Institute (NCI) 
(En español)
The lead federal agency for cancer-related research, training, and health information for the public. Programs at the National Cancer Institute (NCI) focus on the cause, diagnosis, prevention, and treatment of cancer; rehabilitation from cancer; and continuing care of people with cancer and their families.
National Center for Complementary and Alternative Medicine (NCCAM) (En español)
The primary federal agency for scientific research on the diverse medical and health care systems, practices, and products that are not generally considered part of conventional (Western) medicine.
See Related Term(s): Complementary and Alternative Medicine
National Institute of Allergy and Infectious Diseases (NIAID) (En español)
A federal agency that supports basic and applied research to prevent, diagnose, and treat infectious and immune-mediated illnesses, including HIV/AIDS and other sexually transmitted infections. The Institute also supports medical research studies on tuberculosis (TB), malaria, autoimmune disorders, asthma, allergies, and illnesses from potential bioterrorism agents.
National Institutes of Health (NIH) (En español)
A federal agency that is the largest source of funding for medical research in the world. The National Institutes of Health (NIH) is made up of several institutions, each with a specific research focus, such as a particular disease or body system.
National Library of Medicine (NLM) (En español)
A federal institute that serves as the world’s largest medical library and is the creator of PubMed, MEDLINE, and MedlinePlus. The National Library of Medicine (NLM) collects materials in all areas of biomedicine and health care. NLM makes its resources available around the world, primarily through its electronic information services.
A type of medical research study. In natural history studies, researchers examine how a disease or medical condition develops over time. Researchers follow participants who are at risk for or have a specific disease or condition to determine how specific factors, such as family history, age, and occupational exposure, affect the development or progression of the disease or condition. Data collected during a natural history study also provide information on how best to treat a condition or disease.
Natural Killer (NK) Cell (En español)
A type of lymphocyte. Natural killer (NK) cells contain enzymes that can kill other cells, especially tumor cells and cells infected by viruses.
See Related Term(s): Lymphocyte, White Blood Cell
Nemaline Rod Myopathy (NM) (En español)
Also known as: HIV-Associated Adult-Onset Nemaline Myopathy, Rod Body Disease
A rare neuromuscular disorder characterized by the presence of rod-like structures (nemaline bodies) in the muscle fibers and by muscle weakness. Muscle weakness can occur throughout the body, but is typically most severe in the neck, face, and limbs. Nemaline rod myopathy (NM) in its most severe form can be life-threatening. NM can occur as a complication of HIV infection.
Pertaining to an infant during the first 28 days after birth.
New abnormal growth of tissue. Neoplasms may be benign (not cancerous) or malignant (cancerous). Neoplasms are commonly called tumors.
Inflammation of the kidney.
See Related Term(s): Kidneys
Calculi (stones) in the kidney. Use of some antiretroviral (ARV) drugs may cause nephrolithiasis.
See Related Term(s): Kidneys
Toxic or destructive to the kidneys. Certain antiretroviral (ARV) drugs can have nephrotoxic effects.
See Related Term(s): Kidneys
Sharp, shooting pain along a nerve or group of nerves.
A group of neurological disorders caused primarily by HIV damage to the central and peripheral nervous systems. Examples of neuroAIDS disorders include myelopathy, sensory neuropathy, and AIDS dementia.
See Related Term(s): Central Nervous System, Peripheral Nervous System
Damage or degeneration of the nerves, especially the peripheral nerves. Symptoms of neuropathy depend on which nerves are affected and can include pain, tingling, numbness, or weakness. HIV-related neuropathy may be due to HIV infection or use of certain antiretroviral (ARV) drugs.
See Related Term(s): Peripheral Nervous System
Lower-than-normal number of neutrophils (a type of white blood cell) in the blood. Moderate to severe neutropenia can increase the risk of bacterial and fungal infections. Neutropenia may occur as a result of HIV infection or use of some antiretroviral (ARV) drugs.
See Related Term(s): Neutrophil
A type of white blood cell that fights infection by engulfing and killing foreign substances, such as bacteria.
See Related Term(s): White Blood Cell
New Drug Application (NDA) (En español)
A drug sponsor's request to the Food and Drug Administration (FDA) for approval to sell and market a new drug in the United States. A new drug application (NDA) includes enough information for the FDA to determine whether the new drug is safe and effective; whether the drug’s benefits outweigh its risks; whether the proposed drug label (package insert) is appropriate; and whether the drug manufacturing standards are adequate.
See Related Term(s): Food and Drug Administration
Combination antiretroviral therapy (ART) that does not include antiretroviral (ARV) drugs from the non-nucleoside reverse transcriptase inhibitor (NNRTI) drug class. Excluding NNRTIs from an HIV treatment regimen saves drugs in the NNRTI class for future use.
See Related Term(s): Non-Nucleoside Reverse Transcriptase Inhibitor
Non-Hodgkin Lymphoma (NHL) (En español)
A large group of lymphomas (cancers of the lymphatic system). The many types of non-Hodgkin lymphoma (NHL) are classified according to how fast the cancer spreads. Although the symptoms of NHLs vary, they often include swollen lymph nodes, fever, and weight loss. Certain types of NHLs, such as Burkitt lymphoma and immunoblastic lymphoma, are AIDS-defining cancers in people with HIV.
See Related Term(s): AIDS-Defining Cancer, AIDS-Defining Condition, Lymphoma
A clinical trial designed to show that a new drug (or other treatment) is at least as effective as the drug to which it is compared.
See Related Term(s): Superiority Trial
Non-Occupational Post-Exposure Prophylaxis (nPEP) (En español)
Short-term treatment started as soon as possible after high-risk non-occupational exposure to an infectious agent, such as HIV, hepatitis B virus (HBV), or hepatitis C virus (HCV). Non-occupational exposure refers to exposure to an infectious agent that occurs outside of one’s work. The purpose of non-occupational post-exposure prophylaxis (nPEP) is to reduce the risk of infection.
Non-Steroidal Anti-Inflammatory Drug (NSAID) (En español)
A drug used to control pain and inflammation. Common non-steroidal anti-inflammatory drugs (NSAIDs) include aspirin and ibuprofen.
Combination antiretroviral therapy (ART) that does not include antiretroviral (ARV) drugs from the nucleoside reverse transcriptase inhibitor (NRTI) drug class. Excluding NRTIs from an HIV treatment regimen saves drugs in the NRTI class for future use.
See Related Term(s): Nucleoside Reverse Transcriptase Inhibitor
A family of molecules found in all living cells and viruses. Nucleic acids, which include DNA and RNA, control cellular function and heredity.
See Related Term(s): Deoxyribonucleic Acid, Ribonucleic Acid
Also known as: Nucleic Acid Amplification Test
Any of various laboratory tests used to detect the genetic material of a microorganism, such as HIV, in blood, plasma, or other tissue. The viral load (HIV RNA) test is a type of nucleic acid test (NAT).
See Related Term(s): Viral Load Test
Precursor to a nucleotide. The body converts nucleosides into nucleotides, which are then used to make nucleic acids.
See Related Term(s): Nucleic Acid, Nucleotide
A membrane-bound structure containing a cell's chromosomes. All eukaryotes (all organisms except bacteria and viruses) have a nucleus.
See Related Term(s): Chromosome