The recommended dose ranges widely from 500 mg to 9 g/day dried root or equivalent; however, as there are wide variations in the gingerol concentrations in commercial ginger supplements the effective dosage will depend on the preparation and the indication for use.
• Liquid extract (1:2): 0.7-2.0 mL/day.
• Infusion: 4-6 slices of fresh ginger steeped in boiling water for 30 minutes.
Gastric irritation, heartburn and bloating have been reported in clinical trials. Contact dermatitis of the fingertips has also been reported with topical use.
Controlled studies are not available for many interactions; therefore they are based on evidence of activity and are largely theoretical and speculative.
Due to the herb’s antiplatelet effects there is a theoretical risk of increased bleeding at high doses (> 10 g) although this is not evident clinically. There is no evidence of an interaction with warfarin at the usual dietary and therapeutic intakes, and ginger has been shown not to alter prothrombin times in pooled human plasma collected from male volunteers between the ages of 18 and 57 years. A standardised ginger extract, EV.EXT 33, has demonstrated no significant effect on coagulation parameters or on warfarin-induced changes in blood coagulation in rats and ginger was found not to affect clotting status or the pharmacokinetics or pharmacodynamics of warfarin in healthy human subjects. Avoid high-dose supplements unless under medical supervision.
Theoretically, increased antiplatelet and anti-inflammatory effects may occur with high-dose ginger preparations, but the clinical significance of this is unknown. Caution should be exercised with doses > 10 g — possible beneficial effect.
Contraindications and Precautions
Ginger in high doses is not recommended for children under 6 years of age due to the pungent nature of ginger. However, ginger lollies or ginger ale is sometimes used and a dose of 250 mg every 4 hours for motion sickness is safe.
Commission E suggests people with gallstones consult with their physician before using ginger. People with gastric ulcers or reflux should use this herb with caution. Suspend use of high dose supplements (> 10 g) 1 week before major surgery.