Studies have shown a very high tolerance towards high glutamine intake without any I'll side effect or GI distress. I'm talking 20-40g per day range, or .5g -.7g per kg of bodyweight have been used for brief periods of time. Start around 10g daily, split the dose up if desired, 5g twice per day.
I second the vitamin D3 advice, 1000 IU per every 25-30 lbs of bodyweight. It would be nice to have a baseline 25- Hydroxy level, if so, take a look at your most recent lab work and see if available. Ideally you want your level somewhere between 70 ng/mL - 90 ng/mL, no greater than 100 ng/mL.
If you do have an up to date lab value, or are currently and have been supplementing with vitamin D3, an additional 1000 IU added to your current regimen will add somewhere between 7-10 ng/mL. In order to obtain a value within the desired therapeutic range (70-90 ng/mL) adjust as needed and remain at this dose until next lab work is drawn. There have been very, very, few cases where a patient has had to reduce their vitamin D3 regimen due to elevated, out of range levels. Also, take this fat soluble vitamin with a meal containing a sufficient amount of dietary fat.
**I cringed when typing "fat soluble vitamin", the word "vitamin" should not be correlated with this HORMONE at all. Vitamin D also acts as an epigenetic regulator which if wanting to learn about the importance of the epigenome, cancer prevention and improvement of ones overall health and function, gene expression is a great subject to research.