Your blood is made up of liquid and solids. The liquid part, called plasma, is made of water, salts, and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells, and platelets.

Red blood cells (RBC) deliver oxygen from your lungs to your tissues and organs. White blood cells (WBC) fight infection and are part of your immune system. Platelets help blood to clot when you have a cut or wound. Bone marrow, the spongy material inside your bones, makes new blood cells. Blood cells constantly die and your body makes new ones. Red blood cells live about 120 days, and platelets live about 6 days. Some white blood cells live less than a day, but others live much longer.

There are four blood types: A, B, AB, or O. Also, blood is either Rh-positive or Rh-negative. So if you have type A blood, it's either A positive or A negative. Which type you are is important if you need a blood transfusion. And your Rh factor could be important if you become pregnant - an incompatibility between your type and the baby's could create problems.

Blood tests such as blood count tests help doctors check for certain diseases and conditions. They also help check the function of your organs and show how well treatments are working. Problems with your blood may include bleeding disorders, excessive clotting and platelet disorders. If you lose too much blood, you may need a transfusion.

NIH: National Heart, Lung, and Blood Institute

Your blood contains red blood cells (RBC), white blood cells (WBC), and platelets. Blood count tests measure the number and types of cells in your blood. This helps doctors check on your overall health. The tests can also help to diagnose diseases and conditions such as anemia, infections, clotting problems, blood cancers, and immune system disorders.

Specific types include tests for:

• RBC - the numbers, size, and types of RBC in the blood
• WBC - the numbers and types of WBC in the blood
• Platelets - the numbers and size of the platelets
• Hemoglobin - an iron-rich protein in red blood cells that carries oxygen
• Hematocrit - how much space red blood cells take up in your blood
• Reticulocyte count - how many young red blood cells are in your blood
• Mean corpuscular volume (MCV) - the average size of your red blood cells

The complete blood count (CBC) includes most or all of these. The CBC is one of the most common blood tests.

NIH: National Heart, Lung, and Blood Institute

A1C is a blood test for type 2 diabetes and prediabetes. It measures your average blood glucose, or blood sugar, level over the past 3 months. Doctors may use the A1C alone or in combination with other diabetes tests to make a diagnosis. They also use the A1C to see how well you are managing your diabetes. This test is different from the blood sugar checks that people with diabetes do every day.

Your A1C test result is given in percentages. The higher the percentage, the higher your blood sugar levels have been:

• A normal A1C level is below 5.7%
• Prediabetes is between 5.7 to 6.4%. Having prediabetes is a risk factor for getting type 2 diabetes. People with prediabetes may need retests every year.
• Type 2 diabetes is above 6.5%
• If you have diabetes, you should have the A1C test at least twice a year. The A1C goal for many people with diabetes is below 7. It may be different for you. Ask what your goal should be. If your A1C result is too high, you may need to change your diabetes care plan.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

What is genetic testing?

Genetic testing is a type of medical test that looks for changes, sometimes called variants or mutations, in your DNA. DNA contains the genetic instructions in all living things. Often, these changes have no effect, but sometimes, even a small change in DNA can cause disease or other health conditions.

Genetic tests take a sample of your blood or tissues and check your cells to look for any changes in:

• Genes are parts of DNA found in your cells that carry information that controls what you look like and how your body works. Many genes tell your body how to make proteins, which are needed for your body to work correctly.
  • Genome sequencing is a process that checks all your DNA.
  • Exome sequencing is a process that only checks the parts of your DNA that provide instructions to make proteins.
• Proteins do most of the work in your cells. If there are changes in the amount and activity level of proteins, they might be due to changes in the genes that produce those proteins.
• Chromosomes are thread-like structures in your cells. Each chromosome is made up of DNA tightly packaged around proteins. People usually have 23 pairs of chromosomes that contain all their DNA.

What are the different ways to get genetic tests?

Most of the time, genetic testing is done through your health care provider. This is called clinical testing. It is done to find out about an inherited disorder (passed down through families) and to help make decisions about your care.

Other ways to get genetic testing include:

• Research-based testing is a genetic test done as part of a research study (clinical trial).
• Direct-to-consumer (DTC) testing is a genetic test that allows you to send a DNA sample and get the results. You may do this to learn about your ancestry or your risk for certain diseases.

Why is genetic testing done?

Genetic testing may be done for many different reasons, including to:

• Find genetic diseases in a fetus. This is a type of prenatal testing.
• Screen newborn babies for certain treatable conditions.
• Lower the risk of genetic diseases in embryos that were created using assisted reproductive technology.
• Find out if you carry a gene for a certain disease that could be passed on to your children. This is called carrier testing.
• See whether you are at an increased risk of getting a specific disease. This may be done for a disease that runs in your family.
• Diagnose certain diseases.
• Identify genetic changes that may be causing or contributing to a disease that you were already diagnosed with.
• Help guide your provider in deciding the best medicine and dosage for you. This is called pharmacogenomic testing.
• To check for, monitor, or manage a disease. This is sometimes used to help find the best cancer treatment.
• To confirm the biological father (paternity) of a child, or how much genetic information is shared with other relatives.
• To explore the likelihood of having or developing certain physical traits, such as hair color or facial dimples, or to learn about your ancestry.
• To help advance our understanding of genetic conditions, learn how genes work, and find unknown genes.

How is genetic testing done?

Genetic tests are often done on a blood or cheek swab sample. But they may also be done on samples of hair, saliva, skin, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other tissue. The sample is sent to a laboratory. There, a lab technician will use one of several different techniques to look for genetic changes.

What are the benefits of genetic testing?

The benefits of genetic testing include:

• Helping your provider make recommendations for the management or monitoring of a genetic condition.
• Giving you more information for making decisions about your health and your family's health:
  • If you find out that you are at risk for a certain disease, you might take steps to lower that risk. For example, you may find out that you should be screened for a disease earlier and more often. Or you might decide to make healthy lifestyle changes.
  • If you find out that you are not at risk for a certain disease, then you can talk to your provider about when it would be appropriate to schedule checkups or screenings.
  • A test could give you information that helps you make decisions about having children.
• Identifying genetic disorders early in life so that treatment can start as soon as possible.

What are the drawbacks of genetic testing?

The physical risks of the different types of genetic testing are small. But there can be emotional, social, or financial drawbacks:

• Depending on the results, you may feel angry, depressed, anxious, or guilty. This can be especially true if you are diagnosed with a disease that does not have effective treatments.
• Despite the protections that are in place, you may be worried about genetic discrimination in employment or insurance.
• Genetic testing may give you limited information about a genetic disease. For example, it cannot tell you whether you will have symptoms, how severe a disease might be, or whether a disease will get worse over time.
• Genetic testing results might be inconclusive. For example, you might keep getting negative results or not get an answer at all.
• Some genetic tests may give you results that you didn't expect. For example, if you are tested to check for the cause of a rare disease, and a different variant is found that puts you at increased risk for something else that was previously unknown.
• Some genetic tests are expensive, and health insurance might only cover part of the cost. Or they may not cover it at all.

How do I decide whether to be tested?

The decision about whether to have genetic testing is complex. In addition to discussing the test with your provider, you can meet with a genetic counselor. Genetic counselors have specialized degrees and experience in genetics and counseling. They can help you understand the tests and weigh the risks and benefits. If you do take a test, they can explain the results and make sure that you have the support that you need.

Your blood is living tissue made up of liquid and solids. The liquid part, called plasma, is made of water, salts and protein. Over half of your blood is plasma. The solid part of your blood contains red blood cells, white blood cells and platelets.

Blood disorders affect one or more parts of the blood and prevent your blood from doing its job. They can be acute or chronic. Many blood disorders are inherited. Other causes include other diseases, side effects of medicines, and a lack of certain nutrients in your diet.

Types of blood disorders include:

• Platelet disorders, excessive clotting, and bleeding problems, which affect how your blood clots
• Anemia, which happens when your blood does not carry enough oxygen to the rest of your body
• Cancers of the blood, such as leukemia and myeloma
• Eosinophilic disorders, which are problems with one type of white blood cell.

You have two kidneys. They are fist-sized organs on either side of your backbone above your waist. Your kidneys filter and clean your blood, taking out waste products and making urine. Kidney tests check to see how well your kidneys are working. They include blood, urine, and imaging tests.

Early kidney disease usually does not have signs or symptoms. Testing is the only way to know how your kidneys are doing. It is important for you to get checked for kidney disease if you have the key risk factors - diabetes, high blood pressure, heart disease, or a family history of kidney failure.

Specific kidney tests include:

• Glomerular filtration rate (GFR) - one of the most common blood tests to check for chronic kidney disease. It tells how well your kidneys are filtering.
• Creatinine blood and urine tests - check the levels of creatinine, a waste product that your kidneys remove from your blood
• Albumin urine test - checks for albumin, a protein that can pass into the urine if the kidneys are damaged
• Imaging tests, such as an ultrasound - provide pictures of the kidneys. The pictures help the health care provider see the size and shape of the kidneys, and check for anything unusual.
• Kidney biopsy - a procedure that involves taking a small piece of kidney tissue for examination with a microscope. It checks for the cause of kidney disease and how damaged your kidneys are.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

Your thyroid is a small, butterfly-shaped gland in the front of your neck. It makes hormones that control the way the body uses energy. These hormones affect nearly every organ in your body and control many of your body's most important functions. For example, they affect your breathing, heart rate, weight, digestion, and moods.

Thyroid tests check how well your thyroid is working. They are also used to diagnose and help find the cause of thyroid diseases such as hyperthyroidism and hypothyroidism. Thyroid tests include blood tests and imaging tests.

Blood tests for your thyroid include:

• TSH. It measures thyroid-stimulating hormone. This is usually the first test your healthcare provider will order.
• T3 and T4.They measure the level of the different thyroid hormones in your blood.
• Thyroid antibodies test. It measures certain thyroid antibodies (markers in the blood). This test may help diagnose autoimmune thyroid disorders.

Imaging tests include:

• CT scans
• Ultrasound
• Nuclear medicine tests, including:
  • Thyroid scan. It uses small amounts of radioactive material to create a picture of the thyroid, showing its size, shape, and position. It can help find the cause of hyperthyroidism and check for thyroid nodules (lumps in the thyroid).
  • Radioactive iodine uptake test, or thyroid uptake test. It checks how well your thyroid is working and can help find the cause of hyperthyroidism.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

What is hemophilia?

Hemophilia is a rare bleeding disorder in which the blood does not clot properly. This can lead to problems with bleeding too much after an injury or surgery. You can also have sudden bleeding inside your body, such as in your joints, muscles, and organs.

Your blood contains many proteins called clotting factors that can help form clots to stop bleeding. People with hemophilia have low levels of one of these factors, usually either factor VIII (8) or factor IX (9). How severe the hemophilia is depends on the amount of factor in the blood. The lower the amount of the factor, the more likely it is that bleeding could happen and might lead to serious health problems.

What are the types of hemophilia?

There are several different types of hemophilia. The most common are:

• Hemophilia A (classic hemophilia), which is caused by a lack or decrease of clotting factor VIII (8)
• Hemophilia B (Christmas disease), which is caused by a lack or decrease of clotting factor IX (9)

What causes hemophilia?

Most types of hemophilia are inherited. They are caused by change in one of the genes (also called a mutation) that provides instructions for making the clotting factor proteins. The change may mean that the clotting proteins don't work properly or that they are missing altogether.

These genes are on the X chromosome. You may have one or two X chromosomes:

• People who are born male have one X chromosome (from the mother) and one Y chromosome (from the father). They can get hemophilia if their one X chromosome has the gene change.
• People who are born female have two X chromosomes, one from the father and one from the mother. They usually only get hemophilia if:
  • Both X chromosomes have the gene change OR
  • One X chromosome has the gene change and the other X chromosome is missing or inactive.

  People who are born female who have the gene change on one X chromosome are a "carrier" of hemophilia. Sometimes they may have some symptoms of hemophilia. They can pass the gene change on to their children.

Hemophilia that is not inherited is called acquired hemophilia. It is rare. It happens when your body makes specialized proteins called autoantibodies that attack and disable a clotting factor. This can happen because of pregnancy, immune system disorders, cancer, or allergic reactions to certain medicines. Sometimes the cause is unknown.

Who is at risk for hemophilia?

Hemophilia is much more common in people who were born male since they can get it with a change to the gene on one X chromosome. People who have a family history of hemophilia are also at higher risk.

What are the symptoms of hemophilia?

The signs and symptoms of hemophilia are:

• Bleeding into the joints. This can cause swelling and pain or tightness in the joints. It often affects the knees, elbows, and ankles.
• Bleeding into the skin (which is bruising).
• Bleeding into the muscle and soft tissue, which can cause a build-up of blood in the area (called a hematoma).
• Bleeding of the mouth and gums, including bleeding that is hard to stop after you lose a tooth.
• Bleeding after circumcision.
• Bleeding after having shots, such as vaccinations.
• Bleeding in the head of an infant after a difficult delivery.
• Blood in the urine or stool.
• Frequent and hard-to-stop nosebleeds.

In some cases, severe hemophilia may cause bleeding in the brain. This may cause brain damage and can be life-threatening.

How is hemophilia diagnosed?

To find out if you have hemophilia, your health care provider will:

• Ask about your medical history, including your symptoms and other health conditions you may have.
• Ask about your family history, to find out if you have relatives who have or had hemophilia.
• Do a physical exam to look for signs of hemophilia, such as bruising.
• Do certain blood tests to show if your blood is clotting properly. If it does not, then you will have clotting factor tests to diagnose the cause of the bleeding disorder. These blood tests would show the type of hemophilia and the severity.

There is genetic testing for the factor VIII (8) and factor IX (9) genes. This testing may be used in people who have a family history of hemophilia to:

• Identify people who are carriers before they make decisions about pregnancy
• Test a fetus for hemophilia during pregnancy
• Test a newborn for hemophilia

What are the treatments for hemophilia?

The best way to treat hemophilia is to replace the missing clotting factor so that your blood can clot properly. This is usually done by injecting replacement clotting factor into a vein. The replacement clotting factor may be made from donated human blood. Or it may be made in a lab; this kind is called a recombinant clotting factor.

Replacement clotting factor can help treat a bleeding episode. In more severe cases of hemophilia, you might get the factor on a regular basis to prevent bleeding. You can learn how to inject the factor so that you can do it yourself at home.

There are other medicines to treat hemophilia. They may work by releasing factor VIII (8) from where it is stored in the body tissues, replacing the function of factor VIII (8), or preventing clots from breaking down.

If bleeding has damaged your joints, physical therapy may help them function better.

Good quality medical care from healthcare professionals who know a lot about the disorder can help prevent some serious problems. Often the best choice for care is to visit a hemophilia treatment center (HTC).

Centers for Disease Control and Prevention

What is blood glucose?

Blood glucose, or blood sugar, is the main sugar found in your blood. It is your body's primary source of energy. It comes from the food you eat. Your body breaks down most of that food into glucose and releases it into your bloodstream. When your blood glucose goes up, it signals your pancreas to release insulin. Insulin is a hormone that helps the glucose get into your cells to be used for energy.

What is diabetes?

Diabetes is a disease in which your blood glucose levels are too high. When you have diabetes, your body doesn't make enough insulin, can't use it as well as it should, or both. Too much glucose stays in your blood and doesn't reach your cells. Over time, having too much glucose in your blood can cause serious health problems (diabetes complications). So if you have diabetes, it's important to keep your blood glucose levels within your target range.

What are blood glucose targets?

If you have diabetes, your blood glucose target is the range you try to reach as much as possible. The typical targets are:

• Before a meal: 80 to 130 mg/dL
• Two hours after the start of a meal: Less than 180 mg/dL

Your blood glucose targets may be different, depending on your age, any additional health problems you have, and other factors. Talk with your health care team about the best target range for you.

When and how should I check my blood glucose?

If you have diabetes, you'll likely need to check your blood glucose every day to make sure that your blood glucose numbers are in your target range. Some people may need to check their blood glucose several times a day. Ask your health care team how often you need to check it.

The most common way to check your blood glucose level at home is with a blood glucose meter. A blood glucose meter measures the amount of glucose in a small sample of blood, usually from your fingertip.

Continuous glucose monitoring (CGM) is another way to check your glucose levels. Most CGM systems use a tiny sensor that is inserted under your skin. The sensor measures your glucose level every few minutes. It can show changes in your glucose level throughout the day and night. A CGM system is especially useful for people who take insulin and have problems with low blood glucose.

Your provider will also check your blood glucose with a blood test called an A1C. It checks your average blood glucose level over the past three months. People with diabetes usually have an A1C test at least twice a year. But you may need the test more often if you aren't meeting your diabetes treatment goals.

What happens if my blood glucose level becomes too high?

High blood glucose is called hyperglycemia. Symptoms that your blood glucose levels may be too high include:

• Feeling thirsty
• Feeling tired or weak
• Headaches
• Urinating (peeing) often
• Blurred vision

If you often have high blood glucose levels or symptoms of high blood glucose, talk with your health care team. You may need a change in your diabetes meal plan, physical activity plan, or diabetes medicines.

High blood glucose may also be caused by other conditions that can affect insulin or glucose levels in your blood. These conditions include problems with your pancreas or adrenal glands.

What happens if my blood glucose level becomes low for me?

Hypoglycemia, also called low blood glucose, happens when your blood glucose level drops below what is healthy for you. For many people with diabetes, this means a blood glucose reading lower than 70 mg/dL. Your number might be different, so check with your health care team to find out what blood glucose level is low for you.

Symptoms of low blood glucose tend to come on quickly. The symptoms can be different for everyone, but they may include:

• Shaking
• Sweating
• Nervousness or anxiety
• Irritability or confusion
• Dizziness
• Hunger

Low blood glucose levels can be common in people with type 1 diabetes and people with type 2 diabetes who take certain diabetes medicines. If you think you may have low blood glucose, check your level, even if you don't have symptoms. Low blood glucose can be dangerous and should be treated as soon as possible.

Although it's rare, you can still get low blood glucose without having diabetes. The causes can include conditions such as liver disease, kidney disease, and hormone deficiencies (lack of certain hormones). Some medicines, such as certain heart medicines and antibiotics, can also cause it. See your provider to find out the cause of your low blood glucose and how to treat it.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases

Thalassemias are inherited blood disorders. If you have one, your body makes fewer healthy red blood cells and less hemoglobin. Hemoglobin is a protein that carries oxygen to the body. That leads to anemia. Thalassemias occur most often among people of Italian, Greek, Middle Eastern, Southern Asian, and African descent.

Thalassemias can be mild or severe. Some people have no symptoms or mild anemia. The most common severe type in the United States is called Cooley's anemia. It usually appears during the first two years of life. People with it may have severe anemia, slowed growth and delayed puberty, and problems with the spleen, liver, heart, or bones.

Doctors diagnose thalassemias using blood tests. Treatments include blood transfusions and treatment to remove excess iron from the body. If you have mild symptoms or no symptoms, you may not need treatment. In some severe cases, you may need a bone marrow transplant.

NIH: National Heart, Lung, and Blood Institute

Your bone marrow is the spongy tissue inside some of your bones, such as your hip and thigh bones. It contains immature cells, called stem cells. The stem cells can develop into the red blood cells that carry oxygen through your body, the white blood cells that fight infections, and the platelets that help with blood clotting. If you have a myelodysplastic syndrome, the stem cells do not mature into healthy blood cells. Many of them die in the bone marrow. This means that you do not have enough healthy cells, which can lead to infection, anemia, or easy bleeding.

Myelodysplastic syndromes often do not cause early symptoms and are sometimes found during a routine blood test. If you have symptoms, they may include:

• Shortness of breath
• Weakness or feeling tired
• Skin that is paler than usual
• Easy bruising or bleeding
• Pinpoint spots under the skin caused by bleeding
• Fever or frequent infections

Myelodysplastic syndromes are rare. People at higher risk are over 60, have had chemotherapy or radiation therapy, or have been exposed to certain chemicals. Treatment options include transfusions, drug therapy, chemotherapy, and blood or bone marrow stem cell transplants.

NIH: National Cancer Institute