AG1 (Athletic Greens) Review 2026: Worth the Price?

Serious risks

• The Food and Nutrition Board set no upper limit for B12 because its potential for toxicity is low.

Avoid or ask a doctor first if

• People who regularly take certain medications are told to talk with their health care providers about their B12 status.

Medication interactions

• B12 supplements may interact with some medications. Gastric acid inhibitors and metformin may affect B12 levels.
• Several types of medications might adversely affect B12 levels.

Possible side effects

• The most common complaints are diarrhea, nausea, abdominal cramps, and other digestive upset.

Serious risks

• High intakes may raise urinary oxalate and uric acid, which could contribute to kidney stones, especially in people with renal disorders.
• The best evidence that vitamin C contributes to kidney stones is in patients who already have hyperoxaluria.
• In people with hereditary hemochromatosis, long-term high doses could worsen iron overload and cause tissue damage.
• A few in vitro studies suggested that supplemental oral vitamin C, acting as a pro-oxidant, could cause chromosomal or DNA damage and possibly contribute to cancer.
• In postmenopausal women with diabetes in the Iowa Women's Health Study, supplemental vitamin C of at least 300 mg/day was significantly associated with a higher risk of dying from CVD.

Avoid or ask a doctor first if

• People with hereditary hemochromatosis face a concern about iron overload with chronic high doses.
• The upper limits do not apply to people receiving vitamin C as medical treatment, who should be under a physician's care.
• Infants should get vitamin C only from formula and food.

Medication interactions

• Vitamin C supplements may interact with radiation therapy and with medications, including chemotherapy drugs and statins.
• People taking these medications regularly should talk with their health care providers about vitamin C intake.

Possible side effects

• High zinc intakes can cause nausea, dizziness, headaches, gastric distress, vomiting, and loss of appetite.

Serious risks

• Doses of 50 mg or more taken for weeks can interfere with copper absorption, reduce immune function, and lower HDL cholesterol.
• Very high supplemental doses (142 mg/day) might interfere with magnesium absorption and disrupt magnesium balance.
• According to a few reports, overuse of zinc-containing denture adhesive creams can lead to neurological symptoms and anemia.

Avoid or ask a doctor first if

• The upper limits don't apply to people receiving zinc for medical treatment, who should be under a physician's care.
• Zinc-free denture adhesive formulations are available to prevent the effects linked to zinc-containing creams.

Medication interactions

• Zinc may interact with quinolone antibiotics, tetracycline antibiotics, and penicillamine.
• Some diuretics can lower serum zinc by increasing zinc excretion in urine.
• People taking medications regularly should discuss their zinc status with their health care providers.

Possible side effects

• Stomach upset, loose stools, nausea, and drowsiness are listed as common side effects, and ODS calls them mild.
• NCCIH says some people may get drowsiness, stomach upset, diarrhea, and vomiting.
• Increased heart rate variability has been reported.

Serious risks

• There are a few reports of more serious side effects, including effects on liver function.
• In reported liver injury cases, people's conditions improved over time after they stopped the supplement, and some also received medical treatment.
• NCCIH describes liver injury cases linked to ashwagandha supplements and calls them rare.
• Three case reports describe thyrotoxicosis in women taking ashwagandha extract.
• In all three thyrotoxicosis cases, stopping ashwagandha resolved the symptoms.

Avoid or ask a doctor first if

• Some experts advise pregnant women not to use ashwagandha, because some reports suggest it could cause spontaneous abortion.
• NCCIH says to avoid ashwagandha during pregnancy and not to use it while breastfeeding.
• NCCIH does not recommend it before surgery or for people with autoimmune or thyroid disorders.
• People with hormone-sensitive prostate cancer should avoid it because it may raise testosterone.

Medication interactions

• Ashwagandha might interact with thyroid hormone medications.
• It might also interact with antidiabetes drugs, antihypertensives, immunosuppressants, and sedatives.
• NCCIH lists diabetes, high blood pressure, immunosuppressant, sedative, anti-seizure, and thyroid hormone medications.

Possible side effects

• Side effects may include dizziness, headache, insomnia, and either dry mouth or excessive saliva production.
• Rhodiola is possibly safe for up to 12 weeks.

Avoid or ask a doctor first if

• Little is known about safety during pregnancy or breastfeeding.
• People who have or may have depression, or have a family member who may, should consult a health care provider.

Medication interactions

• Interactions between rhodiola and losartan, a blood pressure drug, have been reported.
• People taking any medicine should talk with a health care provider before using an herbal product, since some herbs and medicines interact in harmful ways.

Possible side effects

• Milk thistle taken orally appears to be well tolerated. The most common side effects are digestive symptoms.

Serious risks

• Milk thistle may cause allergic reactions, especially in people allergic to related plants.
• Some supplements have silymarin amounts far from the label, or contain pesticides, microorganisms, or mycotoxins.

Avoid or ask a doctor first if

• People allergic to related plants such as ragweed, chrysanthemum, marigold, and daisy are named as more likely to react.
• Little is known about whether milk thistle is safe during pregnancy or breastfeeding.

Medication interactions

• People taking any medicine should talk with a health care provider before using milk thistle, since some herbs and medicines interact in harmful ways.

Possible side effects

• Insomnia or digestive upsets may occur.

Serious risks

• The source says no serious side effects have been reported.

Avoid or ask a doctor first if

• CoQ10 may not be compatible with some types of cancer treatment.

Medication interactions

• CoQ10 may interact with the blood thinner warfarin and the diabetes drug insulin.

Possible side effects

• Side effects are usually minor and consist of self-limited gastrointestinal symptoms such as gas.

Serious risks

• Probiotic use has been linked to bacteremia, fungemia, and infections that led to severe illness, mostly in severely ill or immunocompromised people.
• Severe or fatal infections have been reported in premature infants given probiotics, and the FDA has warned health care providers.
• In a Boston ICU analysis, 6 of 522 patients given LGG had the ingested LGG found in their blood, versus 2 of 21,652 who did not receive it.
• Possible harms include infections, harmful substances produced by the probiotic microorganisms, and transfer of antibiotic resistance genes.
• Some products have contained microorganisms not listed on the label, which in some instances may pose serious health risks.

Avoid or ask a doctor first if

• For high-risk people such as premature infants or seriously ill hospital patients, the risks of probiotics should be carefully weighed against their benefits.
• For people with compromised immune function or other serious underlying diseases, the WGO advises restricting probiotic use to strains and indications with proven efficacy.
• Consult a health care provider before taking a probiotic supplement, especially with health problems. Anyone with a serious underlying condition should be monitored closely.

Possible side effects

• Stomach upset and diarrhea are the most commonly reported side effects of oral bromelain.
• Oral bromelain seems to be well tolerated.

Avoid or ask a doctor first if

• Safety during pregnancy or breastfeeding is not well known.
• People who take any medicine should talk with a health care provider before using bromelain.

Medication interactions

• The source says some herbs and medicines interact in harmful ways, and advises talking with a provider before using bromelain if you take any medicine. It names no specific drugs.