The UK’s National Institute for Health and Care Excellence has recommended new guidelines for Eliquis users to avoid the risk of life-threatening blood clots.

Eliquis is a type of anticoagulant or blood thinner. Blood thinners like Eliquis are designed to make it harder for a patient to form blood clots. While clotting is a normal part of the healing process, it can misfire, causing blood clots to form within the body. In one form of this, deep vein thrombosis, blood clots form in the large blood vessels of the leg. These clots can dislodge and then travel through the rest of the body, causing stroke, heart attack, or pulmonary embolism depending on where the clot winds up.

National Institute for Health and Care Excellence (NICE), a British/Welsh government agency similar to the U.S. Food and Drug Administration and Centers for Disease Control and Prevention, drafted new guidelines for Eliquis use in early March of 2015. The new guidelines recommend the drug for patients at risk for deep vein thrombosis (DVT) and pulmonary embolism (PE). The committee cited the fact that Eliquis only takes a single daily dose to work, and does not require frequent blood testing or dietary changes. These are positives over older off-patent blood thinners like Warfarin. However, safety concerns about Eliquis abound that could override some of these benefits.

All blood thinners, including Eliquis, carry the risk of working too well. If a patient’s ability to form blood clots is too impaired, they can easily bleed from very minor injuries. When a patient reacts too strongly to a blood thinner, very minor injuries, including internal injuries, become life-threatening. Such uncontrollable bleeding events could include gastrointestinal bleeding, pulmonary bleeding, and brain hemorrhaging. And newer anticoagulants like Eliquis may have risks not seen in older blood thinners.

Older-generation blood thinners like Warfarin and Coumadin worked by interfering with vitamin K. Humans need vitamin K to form blood clots. This meant that patients taking these drugs had to avoid foods with vitamin K, including kale, Brussels sprouts, and other green vegetables. But it also meant that if a patient was taking Warfarin and experienced an uncontrollable bleeding incident, doctors could give them a very large dose of vitamin K to disrupt the drug’s effects. This was called a “reversal” agent. Eliquis currently has no known reversal agents.

Additionally, new research suggests that patients taking newer blood thinners like Eliquis may benefit from blood tests like those used by Warfarin users, possibly undercutting one of Eliquis’s selling points with NICE. This type of blood test can tell if a patient is metabolizing too much or two little of the drug, and can help inform doctors on what dose of Eliquis a patient should take.

NICE’s new guidelines are not finalized, and the draft of these new guidelines is being scrutinized by consultants. Additionally, in an announcement by NICE, the risk of bleeding was being considered at this stage of the process If the draft is approved, these could become the standard recommendations for Eliquis in much of the UK.