Complement is a blood test that measures the activity of certain proteins in the liquid portion of your blood.

The complement system is a group of proteins that move freely through your bloodstream. The proteins work with your immune system and play a role in the development of inflammation.

There are nine major complement proteins. They are labeled C1 through C9.

See also:

• Complement component 3 (C3)
• Complement component 4 (C4)
• CH50
• CH100

Complement assay; Complement proteins

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

There is no special preparation.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Total complement activity (CH50, CH100) looks at the overall activity of the complement system. Typically, other tests that are more specific for the suspected disease are performed first. C3 and C4 are the most commonly measured complement components.

A complement test may be used to monitor patients with an autoimmune disorderand to see if treatment for their condition is working. For example, patients with active lupus erythematosus may have lower-than-normal levels of the complement proteins C3 and C4.

Complement activity varies throughout the body. For example, in patients with rheumatoid arthritis, complement activity in the blood may be normal or higher-than-normal, but much lower-than-normal in the joint fluid.

Patients with gram negative septicemia and shock often have very low C3 and components of what's known as the alternative pathway. C3 is often also low in fungal infections and some parasitic infections such as malaria.

• Total blood complement level: 41 to 90 hemolytic units
• C1 level: 16 to 33 mg/dL
• C3 levels:
  • Males: 88 to 252 mg/dL
  • Females: 88 to 206 mg/dL
• C4 levels:
  • Males: 12 to 72 mg/dL
  • Females: 13 to 75 mg/dL

Note: mg/dL = milligrams per deciliter.

Increased complement activity may be seen in:

• Cancer
• Certain infections
• Ulcerative colitis

Decreased complement activity may be seen in:

• Cirrhosis
• Glomerulonephritis
• Hereditary angioedema
• Hepatitis
• Kidney transplant rejection
• Lupus nephritis
• Malnutrition
• Systemic lupus erythematosus

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

The "complement cascade" is a series of reactions that take place in the blood. The cascade activates the complement proteins. The result is an attack unit that creates holes in the membrane of bacteria, killing them.

The angle or arc that when added to a given angle or arc equals a right angle in measure

That is, for any angle x less than 90º, the complement of xº = (90 - x)º. For example, the complement of 15º is (90 - 15 =) 75º.

Here's a related answer for free: the supplement of an angle x is 180º - x.

Complement C3 is a blood test that measures the activity of a certain protein that is part of the complement system. The complement system is a group of proteins that move freely through your bloodstream. The proteins work with your immune system and play a role in the development of inflammation.

There are nine major complement proteins. They are labeled C1 through C9. This test measures C3.

See also:

• Complement
• C1 inhibiting factor
• Complement component 4 (C4)
• CH50
• CH100

C3

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

There is no special preparation needed.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

C3 and C4 are the most commonly measured complement components.

A complement test may be used to monitor patients with an autoimmune disorderand to see if treatment for their condition is working. For example, patients with active lupus erythematosus may have lower-than-normal levels of the complement proteins C3 and C4.

Complement activity varies throughout the body. For example, in patients with rheumatoid arthritis, complement activity in the blood may be normal or higher-than-normal, but much lower-than-normal in the joint fluid.

Additional conditions under which the test may be performed:

• Fungal infections
• Gram negative septicemia
• Parasitic infections such as malaria
• Paroxysmal nocturnal hemoglobinuria (PNH)
• Shock

The normal range is 75-135 mg/dl (milligrams per deciliter).

Increased complement activity may be seen in:

• Cancer
• Ulcerative colitis

Decreased complement activity may be seen in:

• Bacterial infections (especially Neisseria)
• Cirrhosis
• Glomerulonephritis
• Hepatitis
• Hereditary angioedema
• Kidney transplant rejection
• Lupus nephritis
• Malnutrition
• Systemic lupus erythematosus

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

The "complement cascade" is a series of reactions that take place in the blood. The cascade activates the complement proteins. The result is an attack unit that creates holes in the membrane of bacteria, killing them. C3 attaches to and kills bacteria directly.

Complement component 4 is a blood test that measures the activity of a certain protein that is part of the complement system. The complement system is a group of proteins that move freely through your bloodstream. The proteins work with your immune system and play a role in the development of inflammation.

There are nine major complement proteins. They are labeled C1 through C9. This test measures C4.

See also:

• Complement
• Complement component 3 (C3)
• CH50
• CH100

C4

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

The sample is then sent to the laboratory where the amount of C4 is measured.

No special preparation is needed.

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

If your child is to have this test performed it may be helpful to explain how the test will feel, and even practice or demonstrate on a doll. The more familiar your child is with what will happen to them, and the purpose for the procedure, the less anxiety he or she will feel.

C3 and C4 are the most commonly measured complement components. Complement activity may be measured to determine how severe a disease is or if treatment is working.

A complement test may be used to monitor patients with an autoimmune disorder. For example, patients with active lupus erythematosus may have lower-than-normal levels of the complement proteins C3 and C4.

Complement activity varies throughout the body. For example, in patients with rheumatoid arthritis, complement activity may be normal or higher-than-normal in the blood, but much lower-than-normal in the joint fluid.

• Males: 12 to 72 mg/dL
• Females: 13 to 75 mg/dL

Note: mg/dL = milligrams per deciliter

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about what your specific test results mean.

Increased complement activity may be seen in:

• Cancer
• Ulcerative colitis

Decreased complement activity may be seen in:

• Bacterial infections (especially Neisseria)
• Cirrhosis
• Glomerulonephritis
• Hepatitis
• Hereditary angioedema
• Kidney transplant rejection
• Lupus nephritis
• Malnutrition
• Systemic lupus erythematosus

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

The word complement means "something that completes." (That's why it's spelled complement,as opposed to compliment, a favorable comment.) In geometry, the complement is the angle needed to complete a right angle. Thus,

90° - known quantity = complement

The adjective form of the noun complement is complementary.

The adjective forms of the verb complement are complementing and complemented.

"They consider him a boring speaker."

• object complement (him = speaker)

"He is director of the division."

• subject complement (he = director)

"They made her supervisor of the department."

• object complement (her = supervisor)