This is a single center, double blind randomized cross over design trial that will compare the impact of N-acetyl cysteine (200 mg) vs. saline infusion during experimental hypoglycemia on day one on the responses to experimental hypoglycemia on day two. 18 participants will be studied twice, 8 weeks apart. On each occasion they will undergo a 2 hour hypoglycemic clamp (target 50 mg/dl) in the morning and in the afternoon on day one and then again on the morning of day 2 and day 3. During the morning clamps, samples will be collected for later measurement of serum epinephrine levels, plasma and red blood cell NAC, cysteine, and glutathione concentrations and GSH/GSSG ratios (redox status), and participants will be asked to complete a hypoglycemia symptom questionnaire

This study will consist of a screening visit and two 2-day intervention visits separated by approximately 8 weeks.

At the screening visit, informed consent will be obtained, a standardized form will be used to ensure subjects meet inclusion/exclusion criteria, and baseline hemoglobin A1c will be obtained. On arrival, two IVs will be placed and they will be randomized to receive NAC or saline infusion. Baseline blood samples will be drawn for glucose, epinephrine, norepinephrine, cortisol, cysteine and glutathione measurements. Subjects will then be given 25 mg IV diphenhydramine (Benadryl) followed by a 60 minute infusion of NAC (150 mg) or a similar volume of saline between 8 am and 9 am, followed by a four hour infusion of 50 mg of NAC. Thirty minutes after the start of the NAC infusion, a hyperinsulinemic (2.0 mu/kg/min) hypoglycemic (target = 50 mg/dl) clamp protocol will be started. During the morning study, blood samples will be collected every 5 minutes for monitoring of blood glucose levels and every 15 minutes for later measurement of serum epinephrine, norepinephrine, cortisol. Plasma and red blood cells samples will also be collected every 15 minutes for later measurement of NAC, cysteine, glutathione, and GSH/GSSG ratios (redox status). During the final 15 minutes of the morning clamp, subjects will be asked to quantitate their symptoms using a standardized method (13). At the completion of the morning clamp, glucose will be given to return the participant to euglycemia. 2 hours after the end of the morning clamp, a second hyperinsulinemic (2.0 mu/kg/min) hypoglycemic (target = 50 mg/dl) clamp protocol will be followed over two hours. . The afternoon clamp study will proceed as in the morning except that no serum or plasma will be collected except for the monitoring of glucose and collection of samples for subsequent measurement of NAC, cysteine, glutathione, and GSH/GSSG ratios. After the completion of the afternoon clamps, subjects will be returned to euglycemia and fed a meal. They will be discharged home.

At 7 AM the following morning they will under a single 2 hour hyperinsulinemic hypoglycemic stepped clamp (75, 65, 55,45 mg/dl targets) during which blood samples will be collected as on the morning of day 1. Symptom scores will be collected in the final 15 minutes of each step in the clamp.

At the completion of the study on day 2 of Part 1, they will be scheduled to return for Part 2 in 8 weeks. This timing is selected to ensure that female participants are studied at the same phase of the menstrual cycle. During Part 2 they will receive the treatment not provided during Part 1 in a blinded fashion. The rest of the study protocol will be the same as in Part 1.

Inclusion Criteria:

• Healthy controls
• Age 18 - 65 years
• Baseline hemoglobin A1C <6.0%

Exclusion Criteria:

• History of stroke, seizures (other than those related to hypoglycemia), arrhythmias, active cardiac disease (all of which could be associated with adverse cardiac or neurological events during hypoglycemia)
• Pregnancy or plan to become pregnant during the study period
• Diagnosis of asthma (increases risk of hypersensitivity reactions to NAC)
• Use of anti-oxidants or drugs that can alter glucose metabolism
• Concomitant medical problems that may prevent the subject from successfully completing the protocol
• Unwillingness to avoid exercise during the 7 days before each part of the study