Bochkov DV, Sysolyatin SV, Kalashnikov AI, Surmacheva IA (January 2012). "Shikimic acid: review of its analytical, isolation, and purification techniques from plant and microbial sources". Journal of Chemical Biology. 5 (1): 5–17. doi: 10.1007/s12154-011-0064-8. PMC 3251648. PMID 22826715. Age: Older dogs may require lower doses due to decreased ability to produce melatonin naturally through the pineal gland as they age. Diabetes medications. Melatonin might affect sugar levels. If you take diabetes medications, talk to your doctor before using melatonin.

Until its identification in plants in 1987, melatonin was for decades thought to be primarily an animal neurohormone. When melatonin was identified in coffee extracts in the 1970s, it was believed to be a byproduct of the extraction process. Subsequently, however, melatonin has been found in all plants that have been investigated. It is present in all the different parts of plants, including leaves, stems, roots, fruits, and seeds, in varying proportions. [10] [82] Melatonin concentrations differ not only among plant species, but also between varieties of the same species depending on the agronomic growing conditions, varying from picograms to several micrograms per gram. [39] [83] Notably high melatonin concentrations have been measured in popular beverages such as coffee, tea, wine, and beer, and crops including corn, rice, wheat, barley, and oats. [10] In some common foods and beverages, including coffee [10] and walnuts, [84] the concentration of melatonin has been estimated or measured to be sufficiently high to raise the blood level of melatonin above daytime baseline values. Kelesidis T, Kelesidis I, Chou S, Mantzoros CS (January 2010). "Narrative review: the role of leptin in human physiology: emerging clinical applications". Annals of Internal Medicine. 152 (2): 93–100. doi: 10.7326/0003-4819-152-2-201001190-00008. PMC 2829242. PMID 20083828. Dosage Matters: Adhere strictly to dosage recommendations provided by your veterinarian; giving too much or too little can lead to unwanted side effects or reduced effectiveness. Nesbitt AD, Leschziner GD, Peatfield RC (September 2014). "Headache, drugs and sleep". Cephalalgia (Review). 34 (10): 756–66. doi: 10.1177/0333102414542662. PMID 25053748. S2CID 33548757.

Sande, P. H., Álvarez, J., Calcagno, J., & Rosenstein, R. E. (2016). Preliminary findings on the effect of melatonin on the clinical outcome of cataract surgery in dogs. Veterinary Ophthalmology, 19(3), 184–194. Central nervous system (CNS) depressants. Melatonin use with these medications might cause an additive sedative effect. Melatonin receptors | G protein-coupled receptors | IUPHAR/BPS Guide to Pharmacology". www.guidetopharmacology.org . Retrieved 7 April 2017. Higher levels of this important hormone have also been linked to increases in both strength and muscle mass ( 13, 14).

Using human-grade melatonin may also present the risk of adverse reactions due to potential toxicity concerns, as well as inaccurate dosing due to differences between species. For example, xylitol - an artificial sweetener found in some human-grade products - can cause life-threatening hypoglycemia and liver failure in dogs if ingested. Follow dosing guidelines provided by your vet based on factors such as age, weight, and existing health conditions. Salehi B (5 July 2019). "Melatonin in Medicinal and Food Plants" (PDF). Cells. 681. Archived from the original (PDF) on 29 November 2021 . Retrieved 2 July 2021. Hair loss: Research suggests that melatonin may be helpful for dogs with hair loss. In dogs with certain types of alopecia, melatonin may help prevent hair loss, promote regrowth of fur, and encourage the formation of a healthier coat.a b Hardeland R, Poeggeler B, Srinivasan V, Trakht I, Pandi-Perumal SR, Cardinali DP (2008). "Melatonergic drugs in clinical practice". Arzneimittelforschung. 58 (1): 1–10. doi: 10.1055/s-0031-1296459. PMID 18368944. S2CID 38857779. For optimal safety and efficacy, it is advisable to select a melatonin supplement specifically designed for dogs by experienced veterinarians who understand the nuances of canine physiology.