From what I can tell, at least from my oncologist, when IgG is 400 or more, there's no concern about getting a IgG infusion. I'm currently a little low at 368. He said I should be fine since I do hover around 400 as my history. Since I'm not taking any MM Meds that will continue to knock it down, he's expecting my levels will slowly rise over time. I've had another on the forum report that his Ig levels slower recovered to Normal Range after a few years of no MM Meds.

AnnT - Ongoing Induction and Maintenance Meds will lower your IgG. Even though you're above 400, I expect your Doc anticipates the MM Meds will knock your IgG down so you're getting the IgIV to prevent very low values. My Labs report Ig at 603 is Normal Low but my Doc is pleased with 400 and above. I'd be curious to know what level your Doc thinks its recommended at.

I do remember reading one Post about a person having a problem with an IgIV treatment but I don't remember what they said. I'll try to search this Forum.
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From a NIH Study:
Intravenous immunoglobulin induced-nephropathy: a complication of IVIG therapy
Abstract
Since the early 1950s, intravenous immunoglobulin (IVIG) preparations are being used in the treatment of hematologic, neurologic, nephrologic, autoimmune, and immunodeficiency disorders. Infusion of IVIG preparations may cause osmotic-induced acute renal failure. Despite the fact that this entity has been reported previously, it is not a widely appreciated complication. A total of 22 reports involving 52 patients in whom renal failure occurred in association with IVIG infusion. The patients' ages ranged from 20 to 82 years. Thirty patients had preexisting renal insufficiency. Rise in serum creatinine was noted after 1-10 days of IVIG infusion and creatinine returned to baseline within 2-60 days of discontinuation. One developed end stage renal disease. There were four fatalities related to complications of renal failure. Histopathology of renal tissue showed osmotically induced tubular injury (5 patients), tubular vacuolization (2 patients), tubulointerstitial infiltrate (1 patient), and cryoglobulin deposits (1 patient). There appears to be no direct relationship between the development of acute renal failure and the type of IVIG. However, underlying renal insufficiency increases the risk of renal failure. In view of the increasing use of IVIG preparations in medicine, it is imperative that clinicians be aware of this unusual form renal injury.

Another web article:
Who should not take IVIG?
Certain people, including those with IgA (an immunoglobulin) deficiency and antibodies against IgA and a history of hypersensitivity to human immunoglobulin products should not use this medicine. Feb 1, 2023

Interestingly, most all of us MMers will have low IgA due to our treatment.

I received ivig after my sct for about 2 years. I got it monthly after my blood tests if my immunity was low. After about 2 years my immunity was normal. I had no side effects,

Interesting question Wendell thanks for asking it here, my IgG is always low 4.5 and I was going to ask my immunologist about IVIG I’m also IgA kappa that shows 2 pos traces on serum electrophoresis. (Originally one trace) BMB showed modest lymphoid excess so Im classed as MGUS, happy to stay there as long as possible, take care

Before I started treatment, at the time of diagnosis, my Ig levels were off. My IgA was 5915 since I have IgA MM. My IgM was 25 (low normal is 40) and my IgG was 293 (low normal is 600 - 700, varies per Lab). I expect I had MM brewing for years. My last annual was 4 years prior to diagnosis and it had a slightly elevated serum Protein that my Doc at the time did not follow-up on - then I skipped 4 years. During that time, I was not experiencing a higher level of colds. It seems that a life-time of built-up immunity and a 400ish IgG are somewhat of a defense.

Saying this makes we wonder and expect that for people who get a SCT, since their entire immune system has been wiped out, having a strong IgG base through IgIVs is more important. Once a person has a SCT, everything they encounter is a New Bug that the body has to defend against - there's no longer any antibodies to aid in the effort. Therefore, its up to the IgG & IgM (and whatever else makes our immune system) to do the job.

Note - I did not get an SCT - probably why my Doc is not pushing the IgIV.

I've had infusions several times. No complications. Level was at 400 then up to 700.