Alpha-lipoic acid — contraindications, side effects and what the studies actually show
Alpha-lipoic acid has a single absolute contraindication in the leaflet for the injectable form, but several precautions that really matter: hypoglycaemia in people taking diabetes medicines, a rare autoimmune syndrome and reactions to the infusion. Plus what the ALADIN and SYDNEY trials say — and for whom.
English translation of content medically reviewed in Romanian by Dr. Claudiu Ruscu, intensive care physician (anaesthesia & intensive care)· Romanian text reviewed 13 September 2026
Alpha-lipoic acid has a single absolute contraindication in the summary of product characteristics (SmPC) for the injectable form — hypersensitivity — but several real precautions: hypoglycaemia in people taking insulin or diabetes medicines, insulin autoimmune syndrome, allergic reactions to the infusion, and pregnancy. Oral supplements such as ALA600-SOD contain the same main ingredient, so the same precautions apply, at a different exposure.
What alpha-lipoic acid is
Alpha-lipoic acid — called thioctic acid in medicine leaflets — is a molecule the body produces itself and which works as a cofactor for certain mitochondrial enzymes involved in energy production. It also has antioxidant properties.
In Romania you come across it with two different statuses, and the difference matters:
- as a medicine, dispensed on prescription, in injectable and tablet forms — for example, the 600 mg in 24 ml solution for injection;
- as a food supplement, in tablets or capsules, alone or in combinations.
The authorised indication of the injectable medicine is a single one: severe symptoms of diabetic sensorimotor peripheral polyneuropathy. The regimen in the summary of product characteristics is 600 mg a day intravenously for 2–4 weeks, followed by oral treatment.
What the studies show — and for whom
Alpha-lipoic acid is one of the few "antioxidants" with serious randomised trials of intravenous administration. But all of them concern the same situation: patients with diabetes and symptomatic polyneuropathy.
- ALADIN (1995) — 328 patients with type 2 diabetes, daily infusions for three weeks. The 600 mg dose reduced the foot symptom score more than placebo. At 1,200 mg the effect was no better, but adverse events were more frequent: 32.6%, compared with 18.2% at 600 mg and 20.7% on placebo.
- SYDNEY (2003) — 120 patients, 14 infusions of 600 mg. The symptom score improved by an average of 5.7 points, compared with 1.8 points on placebo.
- The 2004 meta-analysis — four trials, 1,258 patients, with the same three-week regimen. The response rate was 52.7% versus 36.9% on placebo, with no difference in the frequency of adverse events. Worth noting: the trials were selected from the manufacturer's database.
- NATHAN 1 (2011) — oral treatment, 600 mg a day, for four years, in 460 patients. The primary efficacy endpoint showed no difference from placebo; some secondary endpoints were better. Serious adverse events were reported in 38.1% of the treated group, compared with 28.0% on placebo.
What follows from this and what does not: there is evidence for an improvement in some neuropathic symptoms, in the short term, in patients with diabetes. Nothing follows about energy, anti-ageing, weight loss or "inflammation" in general in a person without this disease.
Oral or intravenous — what is the difference
The authorised regimen for the medicine uses both, in stages: an initial intravenous phase, 2–4 weeks, then oral maintenance treatment, 300–600 mg a day, because diabetic polyneuropathy is a chronic disease.
The trials reflect the same logic. The clearest effect on symptoms was measured after the three-week infusions. The four-year oral treatment in NATHAN 1 did not meet its primary endpoint. That does not make the oral route useless, but it shows that the results of one regimen do not automatically transfer to another.
For oral supplements taken without a specific disease, there are no comparable studies showing a clinical benefit.
Contraindications and precautions
| Situation | What the documentation says | What it means in practice |
|---|---|---|
| Hypersensitivity to thioctic acid | Contraindication | Not given |
| Insulin or oral diabetes medicines | The blood-glucose-lowering effect may be potentiated | Risk of hypoglycaemia; blood glucose is monitored, and any adjustment of treatment is made by the doctor |
| Pregnancy | Not to be used unless the clinical condition requires it | We do not give it in pregnancy |
| Breastfeeding | It is not known whether it passes into breast milk | The decision is made with your treating doctor |
| Treatment with cisplatin | The effect of cisplatin may be reduced | Not without the oncologist's agreement |
| Regular alcohol consumption | Reduces effectiveness in neuropathy | Extra caution, see thiamine |
| Under 18 | Safety not established | We do not give it |
Insulin autoimmune syndrome — rare, but worth knowing
During treatment with thioctic acid, cases of insulin autoimmune syndrome have been reported: the body produces antibodies against its own insulin, and the result is episodes of spontaneous hypoglycaemia, including in people without diabetes.
The risk is linked to certain genetic variants of the HLA system. The leaflet mentions that one of them, HLA-DRB1*04:03, occurs in people of European origin, with a higher frequency in southern Europe.
The European Food Safety Authority examined the subject in 2021, starting from 49 case reports, and concluded that alpha-lipoic acid added to foods, including supplements, probably increases the risk in people with these genetic variants, who cannot be identified without testing. In all the cases analysed, the syndrome resolved within a few weeks or months after administration was stopped. A dose below which the risk disappears could not be established.
In practice: if you get dizziness, sweating, tremor or a feeling of fainting while you are taking alpha-lipoic acid, measure your blood glucose and tell your doctor.
Thiamine deficiency — a precautionary measure
Here the level of evidence needs to be stated. The precaution regarding vitamin B1 (thiamine) deficiency does not appear in the summary of product characteristics we consulted. It comes from an animal observation from 1965: in thiamine-deficient rats, alpha-lipoic acid was toxic, and thiamine cancelled out the effect.
There are no human clinical data confirming the risk. But in people in whom thiamine deficiency is plausible — chronic alcohol use, malnutrition, prolonged vomiting, bariatric surgery — the doctor assesses the situation before administration. It is prudence, not a documented contraindication.
Side effects, by frequency
From the summary of product characteristics for the solution for injection:
- common — headache and difficulty breathing after rapid intravenous administration, which resolve on their own; that is why the injection takes at least 12 minutes;
- uncommon — nausea, vomiting, metallic taste;
- very rare — hypoglycaemia, dizziness, sweating, visual disturbances, seizures, purpura, injection-site reactions;
- frequency not known — insulin autoimmune syndrome, systemic allergic reactions including shock, hives, itching, rashes.
There is also one effect with no clinical relevance, but which frightens people: an unusual smell of the urine. The solution is sensitive to light and is protected until it is given.
ALA600-SOD and other supplements
ALA600-SOD is a food supplement, not a medicine: it contains alpha-lipoic acid, superoxide dismutase, vitamin E and selenium. Products of this kind have their place, and the question about side effects is legitimate.
The short answer: the alpha-lipoic acid component carries the same precautions — hypoglycaemia in people taking diabetes medicines and insulin autoimmune syndrome; the 2021 European opinion referred explicitly to supplements. For the other ingredients, read the label and ask the pharmacist, especially if you also take other supplements with vitamin E or selenium.
One more thing, from the leaflet: severe poisoning has been reported after accidental or deliberate ingestion of very large oral doses, of 10–40 g, combined with alcohol. Keep the tablets away from children.
How we work
At Synerva, alpha-lipoic acid appears in a single protocol: Anti-inflammatory, composed of MSM + alpha-lipoic acid, 450 RON, about 60 minutes, after a medical assessment. We do not give it on its own.
Two things said plainly. We do not treat diabetic neuropathy — if you have numbness, burning or pain in your feet and you have diabetes, the place for that conversation is with a diabetologist or neurologist. And if you take insulin or oral diabetes medicines, tell us from the start; it may change the decision.
More about the substance: alpha-lipoic acid.
Sources
For information only. It does not replace a medical consultation and does not recommend changing any diabetes treatment; any adjustment is made by the doctor.
Frequently asked questions
- What are the contraindications of alpha-lipoic acid?
- The absolute contraindication in the summary of product characteristics for the injectable form is hypersensitivity to thioctic acid. The important precautions are treatment with insulin or diabetes medicines (risk of hypoglycaemia), pregnancy, treatment with cisplatin, age under 18 and a history of insulin autoimmune syndrome.
- What side effects does ALA600-SOD have?
- ALA600-SOD is a food supplement containing alpha-lipoic acid, superoxide dismutase, vitamin E and selenium. For the alpha-lipoic acid component, the reactions described include nausea, a metallic taste, rarely hypoglycaemia and, very rarely, insulin autoimmune syndrome. For the complete product, read the label and ask the pharmacist.
- Does alpha-lipoic acid lower blood glucose?
- It can potentiate the effect of insulin and of oral diabetes medicines, which is why the leaflet recommends monitoring blood glucose at the start of treatment. Separately, it can rarely trigger insulin autoimmune syndrome, with spontaneous hypoglycaemia even in people without diabetes.
- What is insulin autoimmune syndrome?
- A rare condition in which the body produces antibodies against its own insulin, with episodes of hypoglycaemia. EFSA analysed 49 cases associated with alpha-lipoic acid; the risk is higher with certain HLA genetic variants, and in all cases it resolved after administration was stopped.
- Can alpha-lipoic acid be taken in pregnancy?
- The leaflet for the injectable form says it should not be used in pregnancy unless the clinical condition of the pregnant woman requires it. We do not give it in pregnancy; during breastfeeding, the decision is made with your treating doctor.
- Does an alpha-lipoic acid infusion help diabetic neuropathy?
- The ALADIN and SYDNEY trials and the 2004 meta-analysis showed an improvement in neuropathic symptoms after three weeks of 600 mg infusions, in patients with diabetes. It is a medical treatment decided by a diabetologist or neurologist. Synerva does not treat neuropathy.
- What does thiamine have to do with alpha-lipoic acid?
- There is an animal observation, from 1965, in which alpha-lipoic acid was toxic to thiamine-deficient rats. There are no human clinical data, but in people at risk of deficiency — chronic alcohol use, malnutrition — the doctor assesses the situation beforehand.
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