Blood Testing

If you take methotrexate for your psoriasis, chances are you'll get regular blood tests. Here's why.

Methotrexate works by slowing down cells that grow too fast—like the skin cells that cause the inflammation and flaking of psoriasis. However, methotrexate can sometimes lead to serious side effects, including:

• Liver damage
• A decrease in red blood cells that carry oxygen throughout the body (anemia)
• A decrease in white blood cells, which may make people more susceptible to infection
• A decrease in platelets that help promote blood clotting

To detect potential side effects before they become serious, doctors usually want to closely monitor patients taking methotrexate with regular blood tests. Those tests—usually done every 4 weeks—check liver function and blood cell counts. Although doctors have been using methotrexate to treat psoriasis since the 1960s, methotrexate is derived from a plant that was used to treat psoriasis by the ancient Egyptians thousands of years ago.