An apparatus for measuring a concentration of a substance in an eye (13) includes a measurement light source (4) producing a measurement light beam having a first wavelength at which the substance has a non-zero first absorption coefficient. The apparatus further includes a reference light source (6) producing a reference light beam having a second wavelength at which the substance has a second absorption coefficient which is substantially equal to zero. At least a portion of the measurement light beam retro-reflects from the retina (17) and at least a portion of the reference light beam retro-reflects from the retina (17). The apparatus further includes a detector (9) responsive to light having the first wavelength by generating a measurement signal and responsive to light having the second wavelength by generating a reference signal.

A skin penetrating system is provided with a drive force generator and a disposable housing member. A plurality of penetrating members are positioned in the disposable housing member. Each penetrating member is coupled to the drive force generator. A plurality of analyte detecting members are each associated with a penetrating member and are positioned in the disposable housing member. Each analyte detecting member is positioned in a sample chamber. The sample chambers have openings for transport of a body fluid into the sample chamber. Each analyte detecting member is configured to determine a concentration of an analyte in a body fluid. A user interface is configured to relay at least one of, skin penetrating performance or a skin penetrating setting.

A blood testing apparatus includes a device for withdrawing blood, a membrane-type testing element, an evaluating device, and a display device forming a complete system which can be manipulated as a single piece of apparatus. Multiple testing elements can be inserted into the apparatus and brought successively to a work position for carrying out several measurements. The blood withdrawing device includes multiple pricking elements. One pricking element is pushed through one testing element and pricks the surface of the skin of a user. The pricking position is disposed so that blood withdrawn from the surface of the skin can impinge upon the testing element.

A device is provided for use with a body fluid sampling device for extracting bodily fluid from an anatomical feature. The device comprises a cartridge having a plurality of cavities. The device may include a plurality of penetrating members each at least partially contained in the cavities of the cartridge wherein the penetrating members are slidably movable to extend outward from openings on the cartridge to penetrate tissue. The device may also include a plurality of analyte detecting members and a plurality of chambers. Each chamber may be associated with one of the cavities, the chambers positioned along an outer periphery of the cartridge, wherein at least one of said analyte detecting members forms a portion of one wall of one of said plurality of chambers. In one embodiment, the device may also include a fluid spreader positioned over at least a portion of said analyte detecting member to urge fluid toward one of the detecting members.

A skin penetrating system includes a housing member and a penetrating member positioned in the housing member. An analyte detecting member is coupled to a sample chamber. The analyte detecting member is configured to determine a concentration of an analyte in a body fluid using a sample of less than 1 .mu.L of a body fluid disposed in the sample chamber. A tip of the penetrating member is configured to extend through an opening of the sample chamber.