In brief: Not exactly. Blood actually doesn't get thinned.  what we call blood thinners are agents that decrease the ability of the blood to clot, usually used in people whose blood clots excessively.
Taking B-complex vitamins, which include vitamin B12, can cause urine to have a bright yellow or even orange color, but check with your doctor to be sure that's what is going on in your case. B vitamins are water-soluble vitamins, which means that what your body doesn't use is excreted in your urine. Riboflavin (vitamin B2) is especially likely to cause this color change in urine. Several medications can also turn urine a bright yellow or orange color. Changes in urine color may also signal certain health problems.
The change in urine colour can indicate which food you have eaten, which medicine or supplement you took or a medical problem. These are some of the foods that may change the colour of urine: Dark yellow or orange: carrots.