Avoid in individuals with a known allergy or hypersensitivity to goldenrod, its constituents, or any members from the Asteraceae/Compositae family, such dandelion, goldenrod, ragweed, sunflower, and daisies. A case of allergic contact dermatitis was reported after taking a fluid goldenrod extract by mouth. Multiple allergies have been reported from contact with species from the Asteraceae/Compositae family, to which goldenrod belongs. Allergic reactions to goldenrod have ranged from urticaria ("hives") to rhinoconjunctivitis and bronchial asthma.

Other than allergic reactions, which can manifest as rash, bronchial asthma or rhinoconjunctivitis, there are currently no reported serious adverse effects to goldenrod in the scientific literature. In two drug-monitoring studies, good tolerability of goldenrod was reported in 97-98% of patients during two to four weeks of treatment. Goldenrod may cause heartburn.

Caution is advised in patients with hypertension (high blood pressure) as goldenrod may increase sodium retention. It is classified as an aquaretic compound, which increases the volume of urine without affecting sodium excretion. Also use cautiously in patients with low blood pressure (hypotension). Use cautiously in patients with osteoporosis as goldenrod may increase calcium excretion.

Avoid irrigation therapy with goldenrod and excess amounts of fluid in patients with edema due to kidney or heart conditions.

Goldenrod is not recommended in pregnant or breastfeeding women due to a lack of available scientific evidence. The combination product called Phytodolor® used to treat arthritis containing aspen, ash, and goldenrod is not recommended during pregnancy due to lack of evidence in this patient group.

A species from the same family as goldenrod (Haplopappus heterophyllus) called rayless goldenrod may contain the toxic substance tremetol or tremetone and has been responsible for intoxication of cows and their calves and also for human poisonings after consumption of milk from intoxicated cows. The toxin is excreted in the milk of lactating animals.

There is no proven safe or effective dose of goldenrod. Gargling with a strained and cooled infusion (2-3 teaspoonfuls of dried goldenrod infused in 1 cup of boiling water for 10-15 minutes) three times daily has been taken by mouth. One cup of strained tea (2-3 teaspoonfuls of dried goldenrod infused 1 cup of boiling water for 10-15 minutes) ingested three to four times daily has also been used. Tinctures have also been taken by mouth in doses of 0.5-2 milliliters of fluid extract (1:1 in 25% ethanol) two or three times daily.

There is no proven safe or effective dose of goldenrod in children and use is not recommended. Traditionally, a tea has been given to children 1-4 years of age using 1-2 grams of dried herb; for 4-10 years of age, 2-5 grams of dried herb; and for 10-16 years of age, 4-8 grams of dried herb.

Goldenrod may have anti-inflammatory effects. Caution is advised when combining with other anti-inflammatory agents.

Although not well studied in humans, goldenrod may have diuretic effects and may increase calcium excretion and decrease potassium and sodium excretion.

Although not well studied in humans, goldenrod may lower blood pressure. However, it may also raise blood pressure in some individuals. Consult with a qualified healthcare professional, including a pharmacist, and check for interactions with other blood pressure altering agents.

Goldenrod may increase the amount of drowsiness caused by some drugs. Examples include benzodiazepines such lorazepam (Ativan®) or diazepam (Valium®), barbiturates such as phenobarbital, narcotics such as codeine, some antidepressants, and alcohol. Caution is advised while driving or operating machinery.

Goldenrod may have anti-inflammatory effects. Caution is advised when combining with other anti-inflammatory agents.

Although not well studied in humans, goldenrod may have diuretic effects and may increase calcium excretion and decrease potassium and sodium excretion.

Although not well studied in humans, goldenrod may have hypotensive (blood pressure lowering) effects. However, it may also raise blood pressure in some individuals. Consult with a qualified healthcare professional, including a pharmacist, and check for interactions with other blood pressure altering agents.

Goldenrod may increase the amount of drowsiness caused by some herbs and supplements. Examples include: hops, lavender aromatherapy, and lemon balm. Caution is advised while driving or operating machinery.