Here’s a question almost every client who books a high-dose Vitamin C drip gets asked before we start: “Have you ever been tested for G6PD deficiency, and do you have any history of kidney issues?”
If that question surprised you the first time you heard it, you’re not alone. Most people come in expecting to talk about immune support or how they’ve been feeling, not kidney function or a lab test they’ve never heard of. So here is the plain-language reason behind both questions, exactly the way your nurse would explain it at the chair.
What “high-dose” means
When we talk about a high-dose Vitamin C (HDVC) drip, we mean anything over 10 grams of ascorbic acid administered intravenously in a single session. At Signature Vitality, we offer sessions at 10g, 20g, 30g, and 50g.
To put that in context: the maximum amount of Vitamin C you can absorb from oral supplements at once tops out far below that. The gut simply doesn’t absorb it past a certain threshold. IV delivery bypasses that ceiling entirely, which is why clients and nurses find HDVC meaningful for immune, skin, and antioxidant support in ways that oral Vitamin C cannot match.
That higher concentration is also why a bit of clinical caution applies. The same potency that makes HDVC interesting is why we ask a few questions first.
Our HDVC drips are diluted in Normal Saline and infused at a controlled rate. Sessions at higher doses (25g and above) additionally require physician approval before we proceed. These aren’t hurdles; they’re the standard of care we apply.
The G6PD test
G6PD stands for glucose-6-phosphate dehydrogenase: an enzyme that lives inside red blood cells and helps protect them from oxidative stress. G6PD deficiency is a genetic condition, and it’s more common than most people realize, particularly in individuals with ancestry from sub-Saharan Africa, the Mediterranean, or parts of Asia.
For most people, G6PD deficiency causes no noticeable issues in day-to-day life. But high-dose intravenous Vitamin C is a significant oxidative load, and for individuals with this deficiency, the red blood cells can respond poorly to that load. For that reason, standard clinical practice in HDVC protocols is to screen for G6PD before sessions over a certain dose threshold.
The test itself is a simple blood draw. Most primary care providers can order it. We screen for it because it’s the right thing to do at doses where it matters, not because we expect a problem. The vast majority of clients we see have no deficiency at all.
- Have you had a G6PD test before, and if so, what was the result?
- Do you have a known family history of the deficiency?
- If we can’t confirm a prior test, we discuss dose options or refer you to your primary care provider to get one ordered before a high-dose session.
Why kidneys come up too
Vitamin C metabolizes primarily through the kidneys. They filter it, process it, and excrete the byproducts in urine. For people with healthy kidney function, this is entirely routine. The kidneys handle the clearance without any issue, and a HDVC session is well-tolerated.
For people with impaired kidney function, the picture is different. The kidneys may not clear the load as efficiently, and certain metabolic byproducts of Vitamin C (oxalate in particular) can accumulate in ways that healthy kidneys clear without trouble. This is why we ask about kidney history and, in some cases, why we’d recommend a conversation with your physician before proceeding at higher doses.
This is not a reason most clients need to worry. Most people who walk through our door have perfectly healthy kidneys and no contraindication to HDVC at any dose we offer. But it is the honest reason the question comes up. You deserve to know why we’re asking, not just be asked.
What we do with your answer
Most of the time, the answer is “no known issues” and we proceed. Your nurse and you decide the appropriate dose together based on your goals, how often you’ve done HDVC before, and what you’re hoping to support. That’s a real clinical conversation, not a checkbox.
We proceed at the dose that makes sense for your goals. First-time HDVC clients often start at 10g or 20g so we can see how you respond, then consider higher doses in future sessions if that's right for you.
We'll recommend a lower dose, discuss alternatives like our standard Vitamin C protocols, or ask you to consult with your primary care provider so we can proceed with their input.
For sessions under the dose threshold, we can often proceed with a conversation. For higher doses, we'll recommend getting tested first: a standard blood draw your primary care provider can order. It's not a barrier; it's a one-time step.
We'll refer you to your physician and discuss alternative protocols that deliver Vitamin C or antioxidant support through approaches that fit your situation. There's almost always something we can do.
This is what “expert IV care” means at Signature Vitality
We could skip these questions. Nothing is forcing us to ask. Some IV bars don’t ask, or bury the answer in a liability waiver no one reads.
We’re nurses with deep IV experience. Our Registered Nurses bring hospital training and real clinical judgment, not technicians running a bag formula. Every protocol we administer is medically supervised: developed and signed off on by a physician, then delivered by RNs who know how to keep the process comfortable and appropriate for you specifically. The intake questions are part of that clinical work.
The kidney question and the G6PD question aren’t bureaucracy. They’re the clinical safety layer that lets us offer HDVC at all, and offer it confidently, at doses that actually matter, to clients who can benefit from them.
When you answer those questions, you’re not clearing a hurdle. You’re getting comfortable, skilled IV care, every visit. That’s the Signature Vitality model.
Other things your nurse might ask, and why
The HDVC intake questions are the ones clients notice most, but they’re not the only ones. Here are a few others that come up, and the same honest reason behind each:
Do you have asthma or use a rescue inhaler regularly?+
Glutathione and NAC (both powerful antioxidants we offer) have a documented consideration for clients with active asthma who use a rescue inhaler above baseline. Your nurse will ask before adding either to your drip. If there's any question, we modify the protocol or skip those ingredients entirely.
What medications are you currently taking?+
Some medications interact with IV nutrients in ways that matter. B-Complex, for example, is something we approach carefully for clients on certain neurological medications. We review your medication list not to be invasive, but because your nurse needs that information to build a session that's actually right for you.
Have you taken any NSAIDs in the last six hours?+
Toradol (ketorolac) is an NSAID we sometimes add as an as-needed pain and inflammation support. Combining it with oral NSAIDs taken recently can increase the load on your stomach and kidneys beyond what we'd want. Six hours is the standard clinical window your nurse applies before adding it.
Every one of these questions is the same trust signal as the kidney question: your nurse is doing her job, not covering a liability. The goal is always to make your session as effective and as appropriate for you as possible.
Questions before you book?
Call or text us and talk to a nurse directly. No sales pitch. Just honest answers about whether HDVC makes sense for you, and what dose would be a reasonable place to start.
