NAD+ Injections: Subcutaneous vs Intramuscular Compared

The difference between NAD+ supplementing that works and NAD+ supplements that disappoint often comes down to a single decision: how you deliver it. Same molecule, dramatically different experiences—and results.

Walk into most longevity clinics and you'll find NAD+ offered three ways: oral supplements, IV infusions, or injections. The pills are convenient but largely ineffective—your digestive system dismantles NAD+ before it reaches your bloodstream. IV therapy works, but requires clinical visits, takes hours, and costs significantly more per session.

NAD+ injections split the difference. You get the bioavailability that makes NAD+ supplementation actually work, without the time commitment or expense of repeated IV sessions. 

But, should the injections be subcutaneous or intramuscular?

Here's what you need to know about subcutaneous vs intramuscular NAD+ injections. 

Why NAD+ Injections Instead of Pills?

Oral NAD+ faces a gauntlet: your stomach. Stomach acid and digestive enzymes break it down. What survives gets processed by your liver before entering circulation, a metabolic screening called first-pass metabolism that destroys some of what you ingested.

The bioavailability challenge with oral NAD+ is significant. 

The molecule is large, unstable in the digestive tract, and subject to extensive breakdown before it can reach systemic circulation. Whether enough intact NAD+ survives to meaningfully raise cellular levels remains an open question.

NAD+ injections bypass this entire problem

When you inject NAD+ subcutaneously or intramuscularly, the molecule reaches your cells in the form they can actually use.

This is why most physicians focused on NAD+ restoration prescribe injections rather than oral supplements. The theoretical advantage is clear, direct delivery eliminates the variables that compromise oral bioavailability.

But which injection is best? 

The Two Routes for NAD+ Injections: Subcutaneous vs Intramuscular

When it comes to NAD+ injections, there are two distinct delivery methods: subcutaneous NAD+ injections and intramuscular NAD+ injections.

What are Subcutaneous NAD+ Injections? 

Subcutaneous injections go into the fatty tissue layer just beneath your skin. 

Think of the area you can pinch on your abdomen, thigh, or upper arm. The needle is short, the injection is shallow, and the NAD+ absorbs gradually through the tissue into your bloodstream over several hours.

What are Intramuscular NAD+ Injections?

Intramuscular injections go deeper, directly into muscle tissue. Common sites include the thigh, glute, or deltoid. The needle is longer, the injection goes deeper, and absorption happens more quickly as the muscle's rich blood supply pulls the NAD+ into circulation faster.

Why the Route Matters

Same molecule. Same goal of restoring cellular NAD+ levels. But the experience of injecting, the absorption timeline, and the practical considerations differ enough that most people develop a clear preference.

The question isn't really which method is "better." Both deliver NAD+ effectively. 

The question is which method fits your body, your comfort level, and your lifestyle. Some people prefer the gentler approach of subcutaneous injection. Others want the faster absorption of intramuscular delivery.

Here's what each method actually feels like, how the absorption differs, and what matters when you're deciding between them.

Subcutaneous NAD+ Injections: The Slow-Release Approach

Subcutaneous NAD+ injections deliver the molecule into your fat layer, where it disperses gradually into your bloodstream.

How SubQ NAD+ Injection Works

You pinch a fold of skin, typically on your abdomen, thigh, or the back of your arm. The needle goes in at a 45 to 90-degree angle, but only about a quarter to half inch deep. You're injecting NAD+ into fat tissue, not muscle. The injection itself takes seconds.

The NAD+ sits in that fatty tissue and absorbs slowly over the next few hours. Think of it as a sustained release rather than an immediate spike.

The Experience

Most people find subcutaneous injections more comfortable than intramuscular. The needle is shorter (usually 25 to 27 gauge, half inch or less). The injection site tends to be less sensitive. You might feel a slight sting, maybe some minor soreness afterward, but it's generally manageable.

Injection sites rotate easily. Abdomen one day, thigh the next. You have multiple spots to choose from, which matters when you're injecting regularly.

Absorption and Duration

Because subcutaneous NAD+ injections absorb gradually, you get a slower rise in NAD+ levels. Some people notice effects building over several hours rather than hitting quickly. The flip side: effects may feel more sustained and even throughout the day.

Who Prefers SubQ

People who are needle-averse or new to injections often start here. The shorter needle and shallower injection feel less intimidating. If you're self-injecting at home for the first time, subcutaneous tends to be the easier learning curve.

It also works well for people who inject frequently. The multiple injection sites and lower discomfort make regular dosing more sustainable.

Intramuscular NAD+ Injections: The Direct Approach

Intramuscular NAD+ injections deliver the molecule directly into muscle tissue, where dense blood flow pulls it into circulation faster.

How IM Injection Works

You inject into muscle, typically the thigh (vastus lateralis), glute (ventrogluteal or dorsogluteal), or shoulder (deltoid). The needle goes in at a 90-degree angle and penetrates deeper, usually one to one and a half inches, depending on the site and your body composition.

This is the type of IM shot you’re familiar with from the doctor’s office for things like flu shots or scheduled vaccines.

The muscle's rich vascular network means NAD+ enters your bloodstream more quickly than with subcutaneous injection. You're trading the gradual diffusion of fat tissue for the rapid uptake of muscle.

The Experience

Intramuscular injections require more confidence. The needle is longer (usually 22 to 25 gauge, one inch or longer). The injection goes deeper. Some people feel more pressure or a sharper sensation during injection. (But remember, it's only like the shots you’d get at the doctors.)

Post-injection soreness is more common with IM. Your muscle has been penetrated, and you might feel it for a day or two afterward, especially if you're new to injecting. Rotating sites helps, but you have fewer options than with subcutaneous.

Absorption and Duration

The muscle's blood supply means faster absorption. Many people report feeling effects within an hour or two rather than waiting several hours. If you want a quicker onset, intramuscular delivers this.

The trade-off is that the faster absorption may mean a shorter duration of noticeable effects, though clinical research on NAD+ pharmacokinetics for different injection routes is limited.

Who Prefers IM

People comfortable with injections often prefer intramuscular. If you've done testosterone or other IM medications before, this feels familiar.

Some people simply respond better to IM. They notice clearer effects, faster onset, and prefer the direct approach even if it means slightly more discomfort. Others find the muscle uptake matches their physiology better than subcutaneous absorption.

Which NAD+ Injection Method Should You Choose?

Both subcutaneous and intramuscular NAD+ injections work. The right choice comes down to practical factors, not efficacy.

Comfort and Needle Anxiety

If you're new to self-injection or have needle hesitation, subcutaneous is the gentler entry point. Shorter needle, shallower depth, less intimidating overall. Once you're comfortable with the process, you can always switch to IM if you want to.

If needles don't bother you or you've injected medications before, intramuscular injection likely won't present any issues.

Absorption Speed Preference

Want a quicker onset? Intramuscular gives you faster absorption and effects you might notice within an hour or two.

Prefer a gradual build that feels more sustained throughout the day? Subcutaneous offers a slower, steadier release.

Injection Frequency and Site Rotation

If you're injecting multiple times per week, subcutaneous offers more site options and generally less soreness between injections. Easier to sustain long-term.

If you're injecting less frequently, intramuscular soreness becomes less of a consideration. You have time to recover between injections.

Individual Response

Here's the honest part: some people simply respond better to one method over the other. Your body composition, your metabolism, and your individual physiology all play a role in how you absorb and utilize NAD+ from different tissue types.

The only way to know which works best for you is to try. Many people start with subcutaneous for ease, then experiment with intramuscular to compare. Others stick with whichever method their physician recommends based on their specific situation.

What the Evidence Shows

Clinical research comparing subcutaneous versus intramuscular delivery specifically for NAD+ is limited. Most pharmacokinetic principles come from broader injection literature across different medications. Both routes deliver NAD+ into systemic circulation. Both bypass the oral bioavailability problems. Whether one produces meaningfully higher NAD+ levels than the other remains an open clinical question.

What we know from patient experience: both methods have advocates, both methods produce results, and personal preference matters more than any theoretical advantage.

The Bottom Line on NAD+ Injections: Subcutaneous vs Intramuscular

Both subcutaneous and intramuscular NAD+ injections solve the fundamental problem with oral NAD+ supplementation: they deliver the molecule intact, bypassing digestive breakdown and first-pass metabolism. Your cells get the NAD+ they need to fuel mitochondrial function, DNA repair, and the cellular processes that decline with age.

The route you choose determines your experience more than your results. 

Subcutaneous injections offer easier administration, more injection sites, and gradual absorption. Intramuscular injections provide faster uptake and work well for people comfortable with deeper injections. Both get NAD+ where it needs to go.

If you're new to NAD+ injection therapy, starting with subcutaneous makes sense for most people.

The right answer isn't universal. It's personal, based on your comfort level, your body's response, and what you can sustain over time. Many physicians prescribe one method initially, then adjust based on how you tolerate it and what you prefer.

Ready to Start NAD+ Injection Therapy?

At Strut Health, physicians prescribe NAD+ injections based on your individual health history, profile, and preferences. You'll also get physician guidance on proper injection technique and dosing.

Everything ships directly to your door. No clinic visits, no waiting rooms, no awkward conversations at the pharmacy.

Take a 5-minute online consultation to see if NAD+ injections are right for you. 

A licensed physician will review your medical history and determine the best approach for your longevity goals.