29 yr male.sr creatinine 0.9 last yr.now 1.1.urineanalysis normal.ultrasound fine.bun12.no bp/diabetes.had vitd&b12 deficiency(3mnths).y this increase?

Insignificant: This is normal lab variation. Repeat it and you're likely to see it fluctuate around 1.0 +/- 0.2. It reflects your state of hydration at the moment of the test and normal variation in the laboratory performing the test. Serum creatinine does not have the precision of an atomic clock! BTW both of your numbers reflect NORMAL glomerular filtration rate which is what creatinine approximates.

Increased muscle...: ...or supplements. The low vitamins would not cause the increase. If you are exercising, you may have increased muscle mass and creatinine is a reflection of muscle mass. If you are taking any supplements with Creatine, that can raise levels. Or, could be normal fluctuation. Bottom line, the 0.2 increase is really not significant to your health and not worth worrying about! Have good health.