Researchers found that the lower the levels of hydroxychloroquine, the greater the rate of clotting events. But the researchers were surprised that when they looked at hydroxychloroquine doses prescribed to patients with lupus compared to the level of hydroxychloroquine in their blood samples, there was no association between the two. This suggests that we likely need to measure hydroxychloroquine levels in a patient’s blood to determine the best dose of the drug to effectively decrease clotting. The anti-malarial drug hydroxychloroquine is one of the few drugs approved by the Food and Drug Administration to treat lupus, and it is one of the essential drugs on the market for this.