I found crystals in my two-week-old son's diaper today. I read that this is a sign of dehydration, but I am feeding him three ounces of breastmilk (through a bottle) every two hours. What's going on?
Urate crystals are orange-red precipitates formed in the bladder, which end up looking like 'brick dust' in a diaper. While they are considered normal in the first few days of life, you are right, they shouldn't be there at two weeks and are a mild, often overlooked sign of dehydration.
The next questions are: Are you sure they are urate crystals? Minute amounts of blood, either from urine or from the skin of the diaper area are sometimes mistaken for crystals. If they really are crystals, and I will take your word for it, then are you sure he is keeping down and absorbing enough liquids? Is he feeding every two hours through the night as well?
Most two-week olds have a total 24-hour intake of about 24 ounces. Is he spitting up a lot? Is he stooling the expected four or more times per day? Is he urinating six or more times a day? And, most importantly, is he gaining good weight? As a general rule of thumb, breastfed babies (or babies drinking breastmilk only) gain an ounce per day for the first two months of life.
Even if all these other signs (urine quantity, stool frequency and weight gain) are reassuring, if you continue to see anything abnormal in his diaper, I would have your pediatrician check it out.
There is also one other possibility, which is that some diapers will leak polymer beads when overly full.