Partial Thromboplastin Time
How It Feels
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
There is very little chance of a problem from
having a blood sample taken from a vein.
- You may get a small bruise at the site. You
can lower the chance of bruising by keeping pressure on the site for several
- In rare cases, the vein may become swollen after the
blood sample is taken. This problem is called phlebitis. A warm compress can be
used several times a day to treat this.
- Ongoing bleeding can be a
problem for people with bleeding disorders. Aspirin, warfarin (such as Coumadin), and
other blood-thinning medicines can make bleeding more likely. If you have
bleeding or clotting problems, or if you take blood-thinning medicine, tell
your doctor before your blood sample is taken.
Partial thromboplastin time (PTT) is a
blood test that measures the time it takes your blood to clot.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Partial thromboplastin time1
| Partial thromboplastin time (PTT):|
| Activated partial thromboplastin time
The heparin dose is changed so that the PTT or APTT
result is about 1.5 to 2.5 times the normal value.1
- A longer-than-normal PTT or APTT can mean a
lack of or low level of one of the blood clotting factors or another substance
needed to clot blood. This can be caused by bleeding disorders, such as
von Willebrand's disease.
longer-than-normal PTT or APTT can be caused by liver disease, kidney disease
nephrotic syndrome), or treatment with blood thinners,
such as heparin or warfarin (Coumadin).
- A longer-than-normal PTT
may be caused by conditions such as antiphospholipid antibody syndrome
or lupus anticoagulant syndrome. These conditions happen when the immune system makes
antibodies that attack blood clotting factors. This
can cause the blood to clot easily in veins and arteries.
- The PTT
can get longer when you are using heparin, so your PTT value needs to be
closely checked. If you have a longer PTT, you may have a higher risk of bleeding.