Evidence check: Human safety studies of NR, NMN and nicotinamide, plus NIH and FDA guidance, checked October 14, 2026. This guide describes what studies reported. It does not set a personal dose or replace advice from someone who knows your health history.
Welcome to Comfort Mind Body. Here, self-care includes the less exciting part: reading the label, asking questions, and knowing when to pause.
Not sure NAD+ is worth trying? Start with our guide to NAD+ benefits. This post is the next step. It shows you how to use NAD+ supplements safely once you have a bottle in your hand.
Most NAD+ ads say little about safety. Many just say the product is “well tolerated.” That may be true, but it leaves out a lot. Who was tested? How much did they take, and for how long?
Below, we cover four things in plain words:
- the side effects people reported in human studies
- who those studies left out
- which medicines to ask about
- what to do if something feels wrong
Key takeaways
- In short human trials, oral NR and NMN caused side effects at rates similar to placebo. Most reported events were mild.
- The longest trials ran about six months. Long-term safety and rare side effects are still unknown.
- Niacin (nicotinic acid) is different: it can cause flushing at 30 mg or more and has a supplement upper limit of 35 mg a day for adults.
- Pregnancy, breastfeeding, cancer, liver disease and several medicines are reasons to check with a clinician first.
- NAD+ injections and IV drips carry separate risks that oral studies do not cover.
- If you think you are reacting, stop, keep the label and lot number, and get advice.
There is no study-backed routine that is safest for everyone. Check the exact product first. Compare it with human studies of the same ingredient and route. Bring the full label and your medicine list to a clinician or pharmacist.
Pause if important questions remain. Short trials can describe common events reported by their participants. They cannot prove that long-term use, a different product, or use with your health conditions is safe.
What side effects have people reported?
In a study, researchers write down every new symptom people have. They do this even if the supplement may not be the cause. Studies call these “adverse events.” In this guide, we just call them side effects.
The best studies also give some people a dummy pill. If both groups have about the same problems, the supplement is less likely to be the cause.
Nicotinamide riboside (NR)
In a 2019 trial of 140 healthy adults with overweight, people took 100, 300, or 1,000 mg of NR, or a dummy pill, every day for eight weeks. Side effects were about the same in every group. No one reported flushing. The company that makes the NR paid for the study.
The NR-SAFE trial (2023) tested a much higher amount: 3,000 mg a day for four weeks. The 20 people in it had Parkinson’s disease. All side effects were mild, and both groups had about the same number.
Two people taking NR had a slower heart rate, but they felt fine. A blood marker called homocysteine went up a little in the NR group. It is linked to how your body uses B vitamins.
The researchers said no one knows if this high amount is safe long term. They advised against taking it outside a study.
Nicotinamide mononucleotide (NMN)
A 2026 review of NMN trials combined the results of 10 studies with 383 adults. The studies lasted from two weeks to six months. Side effects were reported by 58 of 230 people taking NMN and 38 of 153 people taking a dummy pill.
That is not a clear difference. A few serious health problems happened in both groups. The reviewers said there was not enough data to judge those well.
In a 2022 safety trial, 31 healthy adults took 1,250 mg of NMN, or a dummy pill, every day for four weeks. There were five side effects in total. None was serious, and none was clearly caused by NMN.
In a 24-week trial in adults 65 and older, 7 of 31 people taking NMN had side effects, compared with 6 of 29 taking a dummy pill. One person taking NMN left the study after a liver blood test came back high. No one could tell what caused it.
Niacin and nicotinamide
Niacin is vitamin B3. It comes in two main forms, and they act differently. According to the NIH Office of Dietary Supplements, 30 mg or more of nicotinic acid can make your face, arms, and chest turn red.
This is called flushing. It may burn, tingle, or itch. High doses taken for a long time can harm the liver, especially slow-release forms. Adults should not take more than 35 mg of niacin a day from supplements.
Nicotinamide, the other form, does not usually cause flushing. In a 12-month trial of 386 people at high risk of skin cancer, people took 500 mg twice a day. They had about as many side effects as the dummy-pill group.
Some “NAD+” blends add niacin or nicotinamide to NR or NMN, so check the label for both.
Direct NAD+, NADH, nasal sprays, and injections
We found very few safety studies in people on NAD+ or NADH pills, or on NAD+ nasal sprays. When these products say “well tolerated,” the proof often comes from studies of a different ingredient.
Shots and IV drips are a different story. The FDA has warned about reactions such as bad chills, shaking and vomiting after some pharmacy-made NAD+ shots. Our comparison of NR, NMN, niacin, and NAD+ IV explains those options in more detail.
Reported side effects at a glance
On a smaller screen, swipe sideways to see all columns.
| Type | Longest human studies we found | What was reported | Main caution |
|---|---|---|---|
| Oral NR | 8 weeks in healthy adults; 4 weeks at 3,000 mg in Parkinson’s | Mild side effects, about the same as a dummy pill; no flushing | Long-term safety unknown; a small rise in one blood marker at a very high amount |
| Oral NMN | Up to 24 weeks, including adults 65+ | Side effects about the same as a dummy pill; one high liver test with no clear cause | Small studies; not enough data on serious problems |
| Niacin (nicotinic acid) | Decades of use, mainly as a prescription for cholesterol | Red, itchy, tingling skin from 30 mg; liver harm with high doses over time | No more than 35 mg a day from supplements; can affect some medicines |
| Nicotinamide | 12 months at 500 mg twice daily | Side effects about the same as a dummy pill; rarely causes flushing | Counts toward the 35 mg niacin limit |
| Oral NAD+ or NADH | Very few safety studies | Not well known | Safety claims often come from NR or NMN studies |
| NAD+ injection, IV or nasal | A few small studies; none found for nasal sprays | FDA reports of chills, shaking and vomiting after some shots | How it is made and given matters; pill studies do not apply |
What the safety studies cannot tell you yet
Good study results are reassuring. But they only apply to the people and the product that were tested. Here are four big gaps:
- Time: The longest NR and NMN studies lasted about six months. No one knows yet what years of daily use will do.
- Rare harms: Small studies can miss a side effect that affects only 1 person in 1,000.
- Who was left out: Most studies did not include people who were pregnant, breastfeeding, had cancer, or had liver or kidney disease. Many also left out people on several medicines.
- The exact product: A study tests one product from one company. Another brand, a blend, or a bigger dose may act differently.
So “no safety problems found” does not mean “proven safe for you.”
Who should ask a doctor first?
Most of these groups were not studied. Others have a clear reason to be careful. Asking first does not mean you can never take NAD+. It means someone who knows your health should help you decide.
- Pregnant, breastfeeding, or trying to conceive. We found no safety studies of NR or NMN in pregnant or breastfeeding women.
- Current or past cancer. NAD+ gives energy to all cells, including fast-growing cancer cells. In a 2019 mouse study, NMN made cancer grow faster. But in people, nicotinamide lowered new skin cancers in the 12-month study above. The answer for people is not clear yet. Ask your cancer doctor.
- Liver disease. High doses of niacin can harm the liver. One older adult in an NMN study also had a high liver test with no clear cause.
- Kidney disease. Your kidneys help clear what is left after your body uses NAD+. People with kidney disease were mostly left out of studies.
- Autoimmune or inflammatory conditions. Some researchers think more NAD+ could make the immune system more active. This has not been tested in people, so it is worth asking about.
- Upcoming surgery. Tell your surgery team about every supplement you take.
- Under 18. These products have not been tested in children or teens.
- Taking prescription medicines or several supplements. See the medicine section below.
Your 1-minute safety check
Tick anything that applies, then build a short list of questions for your doctor or pharmacist. Nothing is saved or sent anywhere.
Questions to bring to your doctor or pharmacist
Bring the bottle or a photo of every label panel, plus a list of your medicines and supplements. This check helps you start the talk. It is not medical advice.
Can NAD+ supplements interact with medicines?
For niacin, we know which medicines to watch. The NIH lists three:
- Statins. Experts advise against high doses of nicotinic acid if you take a statin for cholesterol.
- Diabetes medicines. High doses of nicotinic acid can raise blood sugar. This can make diabetes medicines work less well.
- Some tuberculosis drugs. Isoniazid and pyrazinamide can lower the niacin in your body.
For NR and NMN, there is no list yet. That is because the research has not been done, not because there are no risks. Many “NAD+” products also contain other ingredients, like resveratrol, quercetin, or extra B vitamins. Each of these can affect medicines in its own way. Ask your pharmacist to check every ingredient on the label, not just the main one.
How to use NAD+ supplements safely: a step-by-step start
Have you and your doctor decided a supplement makes sense? Then start slowly and carefully. That way, if a problem shows up, you will know what caused it.
- Choose one product and one ingredient. Do not take NR, NMN, and an “NAD+ booster” blend all at once.
- Follow the label, not a plan you saw online. The amounts used in studies are not doses meant for you. “More is better” plans have not been tested for safety.
- If the label offers more than one serving size, ask your doctor or pharmacist if you should start with the lower one.
- Change one thing at a time. If you start a new medicine, workout, and supplement in the same week, you cannot tell which one caused a problem.
- Keep a short log for the first two to four weeks. Write down the date, the amount, and anything new. Look for an upset stomach, headaches, sleep changes, flushing, or a racing heart.
- Keep the bottle. The lot number and expiry date help if you need to report a problem.
- Buy from a seller that tests the finished product. Our best NAD supplements guide explains what outside lab testing can and cannot tell you.
- Set a check-in date. Pick a date to ask yourself, or your doctor, if it is helping enough to keep going.
There is no proven best time of day to take it. A small 2022 NMN study in older adults compared morning and afternoon use. It did not find one rule for everyone. If a supplement upsets your stomach, ask if you can take it with food.
Anna’s Note: When I tried Tru Niagen, I started with the PRO 1,000 mg serving for two weeks. Then I switched to the 300 mg serving for two months, and I did just fine on it. That taught me something I now share with everyone who asks: the highest amount on the shelf is not always the better choice. It is worth taking the time to find the amount that works for you, ideally with your doctor or pharmacist. I am one person, so my experience cannot tell you how your body will respond.
What to do if you think you are reacting
The FDA advises that you stop a supplement and seek advice if you think it is causing a problem.
- Get urgent help if you have trouble breathing, a swollen face or throat, chest pain, fainting, or a very fast or uneven heartbeat.
- Stop and call your doctor or pharmacist if a symptom is new, keeps coming back, or worries you. Examples are stomach problems that do not go away, a rash, flushing that does not settle, yellow skin or eyes, or dark urine.
- Do not just cut the dose in half and keep going without advice. A new symptom does not mean the product is “working.”
- Report it. You can tell the FDA about a possible reaction through its Safety Reporting Portal. Reports help the FDA spot problems that small studies miss.
Use the tool below to put the key facts in one place before you call or report.
Build a reaction note
Fill in what you can. You will get a short note. Read it on the phone, show your pharmacist or paste it into an FDA report. Nothing is saved or sent anywhere.
If symptoms are severe, get urgent help first. The note can wait.
Product quality: what a safe bottle looks like
Many supplement problems come from the product, not the ingredient. The bottle may hold the wrong amount, a hidden ingredient, or something unclean. Before you buy, check for:
- a full Supplement Facts label that shows the exact ingredient (for example, “nicotinamide riboside chloride”) and the amount per serving
- the company’s name and contact details
- a lot number, an expiry date, and an unbroken seal
- testing of the finished product by an outside lab, not just a test of the raw powder
- no “proprietary blend” that hides how much of each ingredient you get
- A quality seal tells you something about how a product was made or tested. It cannot tell you that the product will help you or is right for your health. If a label promises to make you “younger,” read our look at whether NAD+ is really the “youth molecule” first.
One more note: the FDA confirmed in September 2025 that NMN can be sold as a dietary supplement. But like all supplements, NR and NMN do not need FDA approval before they are sold.
Frequently asked questions
Final Thoughts
In the short term, NAD+ supplements look fairly safe for healthy adults. That is good news, but it is not the whole story. The studies were small and short. They left out many people who are curious about NAD+. And they tested certain products that may not be the one in your cart.
A safe start is simple. Know what is in the bottle. Check if you should ask a doctor first. Change one thing at a time. And stop if something feels wrong. Still comparing products? Our best NAD supplements guide compares ingredients, testing, and price side by side.
Wondering what “low NAD+” really means? Read what happens when NAD levels drop.
Thank you for taking the careful route. Your body is worth a few extra minutes.
With care,
Anna
Safety Notes
This guide shares general research information. It does not diagnose, give you a dose or replace advice from a doctor or pharmacist who knows your health and medicines. If you think you are having a reaction, stop the supplement and get medical advice. Get urgent help for severe symptoms.
This guide was researched and written by Anna, a self-care writer, using published human studies and NIH and FDA sources. It was not medically reviewed and is not medical advice.
Helpful Resources
- Conze et al., Scientific Reports 2019 — eight-week NR trial in 140 healthy adults with overweight.
- Berven et al., Nature Communications 2023 (NR-SAFE) — 3,000 mg NR daily for four weeks in Parkinson’s disease.
- 2026 systematic review of NMN trials — pooled safety data from 10 trials and 383 adults.
- Fukamizu et al., Scientific Reports 2022 — 1,250 mg NMN daily for four weeks in healthy adults.
- 2026 NMN trial in adults 65 and older — 24-week safety findings.
- Chen et al., New England Journal of Medicine 2015 — 12-month nicotinamide trial for skin cancer prevention.
- Nacarelli et al., Nature Cell Biology 2019 — NAD+ metabolism, inflammation and cancer progression in mice.
- Kim et al., Nutrients 2022 — NMN timing study in older adults.
- NIH Office of Dietary Supplements: Niacin — upper limit, flushing, liver effects and medicine interactions.
- FDA 101: Dietary Supplements — what to do about a suspected reaction.
- HHS Safety Reporting Portal — report a supplement reaction to the FDA.
- FDA notice on compounded NAD+ injections — reported reactions and ingredient quality.
- NutraIngredients, September 2025 — FDA confirms NMN is lawful in dietary supplements.
- NIH: Dietary Supplements, What You Need to Know — questions to ask before taking any supplement.
