Find over 200 print-friendly fact sheets about heart disease and related health topics.
Find definitions for thousands of medical terms, treatments, and tests -- even health-related abbreviations, prefixes, and suffixes.
Some medical tests report results in nanograms (ng) per liter
May 6, 2011
Anne C. Poinier, MD - Internal Medicine & Thomas M. Bailey, MD - Family Medicine
Some medical tests report results in nanomoles (nmol). A mole is an
amount of a substance that contains a large number (6 followed by 23 zeros) of
molecules or atoms. A nanomole is one-millionth of a mole.
Some medical tests report results in nanomoles (nmol) per liter
A narcotic (also called opioid or opiate) is a substance that can
suppress perception of pain and calm the emotional response to pain by reducing
the number of pain signals sent by the nervous system. Narcotics produce a
feeling of well-being (euphoria) and cause mood changes, cloudy thinking, and
Commonly prescribed legal narcotics include butorphanol, codeine, hydrocodone, meperidine,
and morphine. Heroin is an illegal narcotic.
Side effects of narcotics may include constipation and nausea. Frequent use of
narcotics may make a person dependent on them.
January 9, 2013
Anne C. Poinier, MD - Internal Medicine & Nancy Greenwald, MD - Physical Medicine and Rehabilitation
A nasal cannula is a flexible plastic tube that has a set of
two prongs that can be placed in the nostrils. The tube is connected to an
Oxygen passes through the tube, through the
openings in the prongs, and into the nostrils.
April 27, 2011
Sarah Marshall, MD - Family Medicine & Jennifer Merchant, MD - Neonatal-Perinatal Medicine
Nephrologists are medical doctors who specialize in the diagnosis
and treatment of diseases of the kidney and urinary system, such as
inflammation of the kidneys, chronic kidney disease, or cancer.
Nephrologists may further specialize in treating certain age
groups, such as pediatric nephrologists, who only treat children. Nephrologists
may consult with people for short-term illnesses or procedures, such as for a
kidney biopsy. Or they may care for people who have
long-term (chronic) kidney problems or who are on dialysis.
Nephrologists can be board-certified in nephrology through the
American Board of Internal Medicine, which is recognized by the American Board of
August 17, 2012
Anne C. Poinier, MD - Internal Medicine & E. Gregory Thompson, MD - Internal Medicine
Nephrotic syndrome is a warning sign that something is damaging your kidneys. It causes high
levels of protein in the urine and low levels of protein in the
Many things can cause nephrotic syndrome, but the most common are kidney diseases and diabetes.
Nephrotic syndrome will usually get better if the cause is treated. But in some cases, it may lead to long-term kidney problems and kidney failure.
January 4, 2013
Anne C. Poinier, MD - Internal Medicine & Tushar J. Vachharajani, MD, FASN, FACP - Nephrology
A neural tube defect (NTD) is a birth defect that occurs when the
spine, the brain, or the bone and skin that protect them do not develop
properly. The most common type of neural tube defect is spina bifida, in which
the spinal cord or spinal nerves may bulge out through an opening in the bones
of the spine.
The neural tube is the part of a developing fetus that grows into
the spinal cord and brain. Normally, the bones of the skull and spine grow
around the brain and spinal cord, and then skin covers the bones, creating the
neural tube. A neural tube defect occurs when this process doesn't happen
Neural tube defects can be found with prenatal tests, such as
ultrasound and amniocentesis. In spina bifida, treatment depends on the
severity. Surgery may be done to repair the spinal defect or to correct
complications. Physical therapy, braces, and other treatments may be necessary
to help the child with problems resulting from nerve damage.
Anencephaly is the second most common type of neural tube defect.
In anencephaly, the infant is born with only a partially formed brain and
spinal cord. This condition is always fatal.
Neural tube defects may be prevented if a woman takes folic acid
before becoming pregnant and during the first 6 weeks of pregnancy. But often a
woman does not know she is pregnant until after the first 6 weeks of pregnancy.
April 4, 2012
Sarah Marshall, MD - Family Medicine & Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Neurological surgeons are medical doctors who specialize in surgery
of the brain, spinal column, and nervous system.
A person may see a neurological surgeon for a problem such as a
pinched nerve in the back or neck, a brain tumor, or damage to the brain or
spine from an injury. A neurological surgeon may specialize in the treatment of
one area of the body, such as the spinal column, or in the treatment of certain age
groups. One example is a pediatric neurological surgeon, who only treats
Neurological surgeons can be board-certified by the Board of
Neurological Surgery, which is recognized by the American Board of Medical
Neurologists are medical doctors who specialize in the diagnosis
and treatment of brain, spinal cord, and nervous system diseases, such as
multiple sclerosis, Alzheimer's disease, headaches, stroke, or injury.
A neurologist can order or interpret tests such as a computed
tomography (CT) scan, magnetic resonance imaging (MRI), or lumbar puncture to
diagnose problems and may conduct tests to evaluate how well a nerve or muscle
is working. A neurologist can prescribe medicines to treat diseases or may
refer a person to another specialist if needed.
Neurologists can be board-certified by the Board of Psychiatry and
Neurology, which is recognized by the American Board of Medical
Neurotransmitters are chemicals produced by the nerve cells in the
brain that send messages back and forth across the space between the cells
(synapse). When the normal balance of these neurotransmitters is upset,
headache, depression, or other mental health problems may develop.
The neurotransmitters that are believed to play a role in mental
functioning are serotonin, norepinephrine, dopamine, and gamma-aminobutyric
April 5, 2011
Kathleen Romito, MD - Family Medicine & Lisa S. Weinstock, MD - Psychiatry
When people use tobacco products on a regular basis, their bodies
develop a need for nicotine. If they don't get nicotine, they start having
nicotine withdrawal symptoms.
Withdrawal symptoms and cravings for nicotine vary from person to
person. They often depend on how much nicotine a person is used to getting. The
more nicotine the body is used to, the more severe symptoms are likely to be.
Symptoms of withdrawal include feeling:
People going through withdrawal may find it hard to:
Nicotine withdrawal symptoms usually begin about 24 hours after a
person quits smoking or using tobacco products. Symptoms are the worst in the first week or so after the person quits. The average length of time a person deals with withdrawal symptoms is 2 to 3 weeks. The craving for cigarettes and increased appetite can last for
Nicotine replacement products can reduce withdrawal symptoms when used by people who are quitting. Use of quit-smoking medicines, counseling or support groups, a nutritious diet, and regular exercise may also help.
July 6, 2011
Adam Husney, MD - Family Medicine & John Hughes, MD - Psychiatry
Nocturnal hypoglycemia refers to low blood sugar levels at
night in a person who has diabetes. Blood sugar levels can drop below their target
range at night if a person eats too little food after taking his or her usual
nighttime insulin dose or takes more insulin than prescribed in the
Low blood sugar can also happen when there are problems with the insulin (for example, it is expired or it has not been stored properly), when the amount of insulin changes (to find the right amount), or when the person with diabetes is sick.
But sometimes the reason is not obvious. Nocturnal hypoglycemia may also be related to previous exercise or increased physical activity.
Signs of low blood sugar at night include:
Testing blood sugar levels at about 2 a.m. to 3 a.m. for a
few consecutive nights may help a person find out whether low blood sugar is
causing the symptoms. Continuous glucose monitoring (CGM) devices can also help. These devices sound an alarm when blood sugar is too high or too low.
Nocturnal hypoglycemia may be prevented by
decreasing the evening insulin dose or by adding more food to the bedtime
December 4, 2012
John Pope, MD - Pediatrics & Stephen LaFranchi, MD - Pediatrics, Pediatric Endocrinology
Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to relieve
pain and fever and to reduce swelling and inflammation caused by injury or
diseases such as arthritis. Aspirin, ibuprofen, ketoprofen, and naproxen are
commonly used NSAIDs.
NSAIDs may cause side effects. The most common are stomach upset,
heartburn, and nausea. Taking NSAIDs with food may help prevent these problems.
Frequent or long-term use of NSAIDs may lead to stomach ulcers or
high blood pressure. They can also cause a severe allergic reaction.
NSAIDs should be taken exactly as prescribed or according to the
label. Taking a larger dose or taking the medicine longer than recommended can
increase the risk of dangerous side effects.
Talk to your doctor about whether NSAIDs are right for you. People who are older than 65 or who have existing heart, stomach, kidney, liver, or intestinal disease are at higher risk for problems. For other people, the benefits may outweigh the risks.
Aspirin should not be given to anyone younger than 20
because of the risk of Reye syndrome, a rare but serious disease.
December 14, 2011
William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Robert B. Keller, MD - Orthopedics
The normal sinus rhythm is the rate of impulses generated by
certain muscle cells as a signal to the upper heart chambers (atria) to
The heart contains a cluster of specialized muscle cells that act
as the heart's natural pacemaker. This cluster is called the sinoatrial node,
or SA node. The SA node generates the electrical signals that cause the upper
heart chambers (atria) to contract. At rest, the SA node normally sends 60 to
100 impulses per minute (the normal sinus rhythm).
December 14, 2012
Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology & John M. Miller, MD, FACC - Cardiology, Electrophysiology
Nuclear medicine specialists are medical doctors who use radioactive medicines for diagnosis and treatment of certain problems.
Common nuclear medicine tests include bone scans, lung perfusion
scans, and HIDA scans for gallbladder function.
Nuclear medicine specialists can be board-certified through the
Board of Nuclear Medicine, which is recognized by the American Board of Medical
Nurse practitioners (NPs) are registered nurses (RNs) who have
advanced education and clinical training. They can perform physical
exams, diagnose and treat health problems, order lab work and X-rays,
prescribe medicines, and provide health information.
Nurse practitioners may specialize in the care of children
(pediatric nurse practitioner), older adults (geriatric nurse practitioner),
people of all ages (family nurse practitioner), or people with mental health
problems (psychiatric nurse practitioner).
Nurse practitioners are licensed by the state in which they
practice. Most nurse practitioners are nationally certified in their specialty
Nutrients are substances in
food that provide energy or are needed to support normal body functions.
Nutrients are used to build and repair body tissues, including muscles, bones,
and internal organs.
January 25, 2013
Kathleen Romito, MD - Family Medicine & Rhonda O'Brien, MS, RD, CDE - Certified Diabetes Educator