Because nattokinase, serrapeptase, and bromelain don't have any negative side effects for most people, I recommend a very potent dose of all 3 during the first two to four months. Later on, you can drop down to a lower, maintenance dose. Bromelain has more positive research written about it than papain. Nattokinase has more positive research written about it than serrapeptase and bromelain combined. If you can afford only 1 of the 3, then go with nattokinase. Nattokinase is the most certain to fight blood clots and improve circulation. Nattokinase has only positive things written about it. However, there is one negative scientific study on serrapeptase. Serrapeptase was not significantly more effective than placebo in a Japanese study so the Japanese manufacturer of "Dasen" (serrapeptase), Takeda, has pulled this, their profitable brand name drug, off the market. However, thousands of people will testify that serrapeptase has helped them substantially and that they continue to buy it. Bromelain has been used for many years in Germany after surgery with a small but definite benefit. Speaking of surgery, 25% of hip fracture victims die within 12 months after surgery. Many other surgeries have almost as high post-surgery death rates. The most common causes of post-surgery death are blood clots, Pneumonia, and infection. Nattokinase, which has no negative side effects, can definitely be used in place of aspirin, Lovenox, or other prescription blood thinners. Serrapeptase has been described as "the most powerful" of the 3. To prevent infection and Pneumonia, boost your immune system by drinking olive leaf tea, eating shiitake mushrooms, and swallowing at least 2000 IU of vitamin D daily. Vaccinate to help prevent Pneumonia before the surgery. To help nattokinase improve your blood circulation, swallow 1000mg to 1200mg of krill oil daily to boost your HDL (good) cholesterol and clean up your clogged arteries. Half of all heart disease victims have a calcified aorta. To reverse a calcified aorta (to remove the calcium), you will need to eat vitamin K2 MK-7 and vitamin K2 MK-8 from the Japanese fermented soybean food called, "natto." One small 3.5oz package of natto contains 1000mcg of MK-7 and almost 100mcg of MK-8. People with type O blood have the least problems with blood clots because their blood is thinnest. People with type B blood (myself included) have the 2nd thinnest blood. People with type A blood and people with type AB blood have the thickest blood and are most likely to benefit from nattokinase, serrapeptase, and/or bromelain. Indeed, people with blood types A and AB have been known to get blood clots in their legs just for sitting several hours during an airplane flight